Interaction between lut and shared merge list

ABSTRACT

A method for processing video data is provided to include: determining whether a sharing of merge list information is enabled for a merge sharing node that corresponds to an ancestor node in a coding unit split tree to allow leaf coding units of the ancestor node in the coding unit split tree to use the merge list information; and performing a conversion between a current video block of a video and a bitstream of the video based on the determining.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2020/071656, filed on Jan. 13, 2020, which claims the priority toand benefits of International Patent Application No. PCT/CN2019/071510,filed on Jan. 13, 2019. All the aforementioned patent applications arehereby incorporated by reference in their entireties.

TECHNICAL FIELD

This patent document relates to video coding techniques, devices andsystems.

BACKGROUND

In spite of the advances in video compression, digital video stillaccounts for the largest bandwidth use on the internet and other digitalcommunication networks. As the number of connected user devices capableof receiving and displaying video increases, it is expected that thebandwidth demand for digital video usage will continue to grow.

SUMMARY

This document discloses methods, systems, and devices for encoding anddecoding digital video using a merge list of motion vectors.

In one example aspect, a method for video processing is disclosed. Themethod includes determining, whether to use a temporal prediction forobtaining an adaptive loop filter for a conversion between a currentvideo block of a video and a coded representation of the video, based onwhether a cross-tile prediction is enabled; and performing theconversion using an adaptive loop filter that is obtained based on thedetermining.

In another example aspect, a method for video processing is disclosed.The method includes determining whether a sharing of merge listinformation is enabled for a merge sharing node that corresponds to anancestor node in a coding unit split tree to allow leaf coding units ofthe ancestor node in the coding unit split tree to use the merge listinformation; and performing a conversion between a current video blockof a video and a coded representation of the video based on thedetermining.

In yet another example aspect, a video encoder device that implements avideo encoding method described herein is disclosed.

In yet another representative aspect, the various techniques describedherein may be embodied as a computer program product stored on anon-transitory computer readable media. The computer program productincludes program code for carrying out the methods described herein.

In yet another representative aspect, a video decoder apparatus mayimplement a method as described herein.

The details of one or more implementations are set forth in theaccompanying attachments, the drawings, and the description below. Otherfeatures will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of a video encoderimplementation

FIG. 2 illustrates macroblock partitioning in the H.264 video codingstandard.

FIG. 3 illustrates an example of splitting coding blocks (CB) intoprediction blocks (PU).

FIG. 4 illustrates an example implementation for subdivision of a CTBinto CBs and transform block (TBs). Solid lines indicate CB boundariesand dotted lines indicate TB boundaries, including an example CTB withits partitioning, and a corresponding quadtree.

FIG. 5 shows an example of a Quad Tree Binary Tree (QTBT) structure forpartitioning video data.

FIG. 6 shows an example of video block partitioning.

FIG. 7 shows an example of quad-tree partitioning.

FIG. 8 shows an example of tree-type signaling.

FIG. 9 shows an example of a derivation process for merge candidate listconstruction.

FIG. 10 shows example positions of spatial merge candidates.

FIG. 11 shows examples of candidate pairs considered for redundancycheck of spatial merge candidates.

FIG. 12 shows examples of positions for the second PU of Nx2N and 2NxNpartitions.

FIG. 13 illustrates motion vector scaling for temporal merge candidates.

FIG. 14 shows candidate positions for temporal merge candidates, andtheir co-located picture.

FIG. 15 shows an example of a combined bi-predictive merge candidate.

FIG. 16 shows an example of a derivation process for motion vectorprediction candidates.

FIG. 17 shows an example of motion vector scaling for spatial motionvector candidates.

FIG. 18 shows an example Alternative Temporal Motion Vector Prediction(ATMVP) for motion prediction of a CU.

FIG. 19 pictorially depicts an example of identification of a sourceblock and a source picture.

FIG. 20 shows an example of one CU with four sub-blocks and neighboringblocks.

FIG. 21 illustrates an example of bilateral matching.

FIG. 22 illustrates an example of template matching.

FIG. 23 depicts an example of unilateral Motion Estimation (ME) in FrameRate Up Conversion (FRUC).

FIG. 24 shows an example of DMVR based on bilateral template matching.

FIG. 25 shows an example of spatially neighboring blocks used to derivespatial merge candidates.

FIG. 26 depicts an example how selection of a representative positionfor look-up table updates.

FIG. 27A and 27B illustrate examples of updating look up table with newset of motion information.

FIGS. 28A and 28B show examples of hardware platforms for implementing avisual media decoding or a visual media encoding technique described inthe present document.

FIG. 29 is an example of a flowchart for video processing method basedon some implementations of the disclosed technology.

FIG. 30 is an example of a flowchart for video processing method basedon some implementations of the disclosed technology.

FIG. 31 shows an example of a decoding flow chart with the proposed HMVPmethod.

FIG. 32 shows examples of updating tables using the proposed HMVPmethod.

FIGS. 33A and 33B show examples of a redundancy-removal based LUTupdating method (with one redundancy motion candidate removed).

FIGS. 34A and 34B show examples of a redundancy-removal based LUTupdating method (with multiple redundancy motion candidates removed).

FIG. 35 shows an example of differences between Type 1 and Type 2blocks.

DETAILED DESCRIPTION

To improve compression ratio of video, researchers are continuallylooking for new techniques by which to encode video.

1. Introduction

The present document is related to video coding technologies.Specifically, it is related to motion information coding (such as mergemode, AMVP mode) in video coding. It may be applied to the existingvideo coding standard like HEVC, or the standard (Versatile VideoCoding) to be finalized. It may be also applicable to future videocoding standards or video codec.

Brief Discussion

Video coding standards have evolved primarily through the development ofthe well-known ITU-T and ISO/IEC standards. The ITU-T produced H.261 andH.263, ISO/IEC produced MPEG-1 and MPEG-4 Visual, and the twoorganizations jointly produced the H.262/MPEG-2 Video and H.264/MPEG-4Advanced Video Coding (AVC) and H.265/HEVC standards. Since H.262, thevideo coding standards are based on the hybrid video coding structurewherein temporal prediction plus transform coding are utilized. Anexample of a typical HEVC encoder framework is depicted in FIG. 1.

2.1 Partition Structure

2.1.1 Partition tree structure in H.264/AVC

The core of the coding layer in previous standards was the macroblock,containing a 16×16 block of luma samples and, in the usual case of 4:2:0color sampling, two corresponding 8×8 blocks of chroma samples.

An intra-coded block uses spatial prediction to exploit spatialcorrelation among pixels. Two partitions are defined: 16×16 and 4×4.

An inter-coded block uses temporal prediction, instead of spatialprediction, by estimating motion among pictures. Motion can be estimatedindependently for either 16×16 macroblock or any of its sub-macroblockpartitions: 16×8, 8×16, 8×8, 8×4, 4×8, 4×4 (see FIG. 2). Only one motionvector (MV) per sub-macroblock partition is allowed.

2.1.2 Partition Tree Structure in HEVC

In HEVC, a CTU is split into CUs by using a quadtree structure denotedas coding tree to adapt to various local characteristics. The decisionwhether to code a picture area using inter-picture (temporal) orintra-picture (spatial) prediction is made at the CU level. Each CU canbe further split into one, two or four PUs according to the PU splittingtype. Inside one PU, the same prediction process is applied and therelevant information is transmitted to the decoder on a PU basis. Afterobtaining the residual block by applying the prediction process based onthe PU splitting type, a CU can be partitioned into transform units(TUs) according to another quadtree structure similar to the coding treefor the CU. One of key feature of the HEVC structure is that it has themultiple partition conceptions including CU, PU, and TU.

In the following, the various features involved in hybrid video codingusing HEVC are highlighted as follows.

1) Coding tree units and coding tree block (CTB) structure: Theanalogous structure in HEVC is the coding tree unit (CTU), which has asize selected by the encoder and can be larger than a traditionalmacroblock. The CTU consists of a luma CTB and the corresponding chromaCTBs and syntax elements. The size LxL of a luma CTB can be chosen asL=16, 32, or 64 samples, with the larger sizes typically enabling bettercompression. HEVC then supports a partitioning of the CTBs into smallerblocks using a tree structure and quadtree-like signaling.

2) Coding units (CUs) and coding blocks (CBs): The quadtree syntax ofthe CTU specifies the size and positions of its luma and chroma CBs. Theroot of the quadtree is associated with the CTU. Hence, the size of theluma CTB is the largest supported size for a luma CB. The splitting of aCTU into luma and chroma CBs is signaled jointly. One luma CB andordinarily two chroma CBs, together with associated syntax, form acoding unit (CU). A CTB may contain only one CU or may be split to formmultiple CUs, and each CU has an associated partitioning into predictionunits (PUs) and a tree of transform units (TUs).

3) Prediction units and prediction blocks (PBs): The decision whether tocode a picture area using inter picture or intra picture prediction ismade at the CU level. A PU partitioning structure has its root at the CUlevel. Depending on the basic prediction-type decision, the luma andchroma CBs can then be further split in size and predicted from luma andchroma prediction blocks (PBs). HEVC supports variable PB sizes from64×64 down to 4×4 samples. FIG. 3 shows examples of allowed PBs for aMxM CU.

4) TUs and transform blocks: The prediction residual is coded usingblock transforms. A TU tree structure has its root at the CU level. Theluma CB residual may be identical to the luma transform block (TB) ormay be further split into smaller luma TBs. The same applies to thechroma TBs. Integer basis functions similar to those of a discretecosine transform (DCT) are defined for the square TB sizes 4×4, 8×8,16×16, and 32×32. For the 4×4 transform of luma intra picture predictionresiduals, an integer transform derived from a form of discrete sinetransform (DST) is alternatively specified.

FIG. 4 shows an example of a subdivision of a CTB into CBs and transformblock (TBs). Solid lines indicate CB borders and dotted lines indicateTB borders. (a) CTB with its partitioning. (b) corresponding quadtree.

2.1.2.1 Tree-Structured Partitioning into Transform Blocks and Units

For residual coding, a CB can be recursively partitioned into transformblocks (TBs). The partitioning is signaled by a residual quadtree. Onlysquare CB and TB partitioning is specified, where a block can berecursively split into quadrants, as illustrated in FIG. 4. For a givenluma CB of size MxM, a flag signals whether it is split into four blocksof size M/2xM/2. If further splitting is possible, as signaled by amaximum depth of the residual quadtree indicated in the SPS, eachquadrant is assigned a flag that indicates whether it is split into fourquadrants. The leaf node blocks resulting from the residual quadtree arethe transform blocks that are further processed by transform coding. Theencoder indicates the maximum and minimum luma TB sizes that it willuse. Splitting is implicit when the CB size is larger than the maximumTB size. Not splitting is implicit when splitting would result in a lumaTB size smaller than the indicated minimum. The chroma TB size is halfthe luma TB size in each dimension, except when the luma TB size is 4×4,in which case a single 4×4 chroma TB is used for the region covered byfour 4×4 luma TBs. In the case of intra-picture-predicted CUs, thedecoded samples of the nearest-neighboring TBs (within or outside theCB) are used as reference data for intra picture prediction.

In contrast to previous standards, the HEVC design allows a TB to spanacross multiple PBs for inter-picture predicted CUs to maximize thepotential coding efficiency benefits of the quadtree-structured TBpartitioning.

2.1.2.2 Parent and Child Nodes

A CTB is divided according to a quad-tree structure, the nodes of whichare coding units. The plurality of nodes in a quad-tree structureincludes leaf nodes and non-leaf nodes. The leaf nodes have no childnodes in the tree structure (i.e., the leaf nodes are not furthersplit). The, non-leaf nodes include a root node of the tree structure.The root node corresponds to an initial video block of the video data(e.g., a CTB). For each respective non-root node of the plurality ofnodes, the respective non-root node corresponds to a video block that isa sub-block of a video block corresponding to a parent node in the treestructure of the respective non-root node. Each respective non-leaf nodeof the plurality of non-leaf nodes has one or more child nodes in thetree structure.

2.1.3 Quadtree Plus Binary Tree Block Structure with Larger CTUs in JEM

To explore the future video coding technologies beyond HEVC, Joint VideoExploration Team (JVET) was founded by VCEG and MPEG jointly in 2015.Since then, many new methods have been adopted by JVET and put into thereference software named Joint Exploration Model (JEM).

2.1.3.1 QTBT Block Partitioning Structure

Different from HEVC, the QTBT structure removes the concepts of multiplepartition types, i.e. it removes the separation of the CU, PU and TUconcepts, and supports more flexibility for CU partition shapes. In theQTBT block structure, a CU can have either a square or rectangularshape. As shown in FIG. 5, a coding tree unit (CTU) is first partitionedby a quadtree structure. The quadtree leaf nodes are further partitionedby a binary tree structure. There are two splitting types, symmetrichorizontal splitting and symmetric vertical splitting, in the binarytree splitting. The binary tree leaf nodes are called coding units(CUs), and that segmentation is used for prediction and transformprocessing without any further partitioning. This means that the CU, PUand TU have the same block size in the QTBT coding block structure. Inthe JEM, a CU sometimes consists of coding blocks (CBs) of differentcolour components, e.g. one CU contains one luma CB and two chroma CBsin the case of P and B slices of the 4:2:0 chroma format and sometimesconsists of a CB of a single component, e.g., one CU contains only oneluma CB or just two chroma CBs in the case of I slices.

The following parameters are defined for the QTBT partitioning scheme.

-   CTU size: the root node size of a quadtree, the same concept as in    HEVC-   MinQTSize: the minimally allowed quadtree leaf node size-   MaxBTSize: the maximally allowed binary tree root node size-   MaxBTDepth: the maximally allowed binary tree depth-   MinBTSize: the minimally allowed binary tree leaf node size

In one example of the QTBT partitioning structure, the CTU size is setas 128×128 luma samples with two corresponding 64×64 blocks of chromasamples, the MinQTSize is set as 16×16, the MaxBTSize is set as 64×64,the MinBTSize (for both width and height) is set as 4×4, and theMaxBTDepth is set as 4. The quadtree partitioning is applied to the CTUfirst to generate quadtree leaf nodes. The quadtree leaf nodes may havea size from 16×16 (i.e., the MinQTSize) to 128×128 (i.e., the CTU size).If the leaf quadtree node is 128×128, it will not be further split bythe binary tree since the size exceeds the MaxBTSize (i.e., 64×64).Otherwise, the leaf quadtree node could be further partitioned by thebinary tree. Therefore, the quadtree leaf node is also the root node forthe binary tree and it has the binary tree depth as 0. When the binarytree depth reaches MaxBTDepth (i.e., 4), no further splitting isconsidered. When the binary tree node has width equal to MinBTSize(i.e., 4), no further horizontal splitting is considered. Similarly,when the binary tree node has height equal to MinBTSize, no furthervertical splitting is considered. The leaf nodes of the binary tree arefurther processed by prediction and transform processing without anyfurther partitioning. In the JEM, the maximum CTU size is 256×256 lumasamples.

FIG. 5 (left) illustrates an example of block partitioning by usingQTBT, and FIG. 5 (right) illustrates the corresponding treerepresentation. The solid lines indicate quadtree splitting and dottedlines indicate binary tree splitting. In each splitting (i.e., non-leaf)node of the binary tree, one flag is signalled to indicate whichsplitting type (i.e., horizontal or vertical) is used, where 0 indicateshorizontal splitting and 1 indicates vertical splitting. For thequadtree splitting, there is no need to indicate the splitting typesince quadtree splitting always splits a block both horizontally andvertically to produce 4 sub-blocks with an equal size.

In addition, the QTBT scheme supports the ability for the luma andchroma to have a separate QTBT structure. Currently, for P and B slices,the luma and chroma CTBs in one CTU share the same QTBT structure.However, for I slices, the luma CTB is partitioned into CUs by a QTBTstructure, and the chroma CTBs are partitioned into chroma CUs byanother QTBT structure. This means that a CU in an I slice consists of acoding block of the luma component or coding blocks of two chromacomponents, and a CU in a P or B slice consists of coding blocks of allthree colour components.

In HEVC, inter prediction for small blocks is restricted to reduce thememory access of motion compensation, such that bi-prediction is notsupported for 4×8 and 8×4 blocks, and inter prediction is not supportedfor 4×4 blocks. In the QTBT of the JEM, these restrictions are removed.

2.1.4 Ternary-Tree for VVC

Tree types other than quad-tree and binary-tree are supported. In theimplementation, two more ternary tree (TT) partitions, i.e., horizontaland vertical center-side ternary-trees are introduced, as shown in FIG.6(d) and (e).

FIG. 6 shows: (a) quad-tree partitioning (b) vertical binary-treepartitioning (c) horizontal binary-tree partitioning (d) verticalcenter-side ternary-tree partitioning (e) horizontal center-sideternary-tree partitioning.

There are two levels of trees, region tree (quad-tree) and predictiontree (binary-tree or ternary-tree). A CTU is firstly partitioned byregion tree (RT). A RT leaf may be further split with prediction tree(PT). A PT leaf may also be further split with PT until max PT depth isreached. A PT leaf is the basic coding unit. It is still called CU forconvenience. A CU cannot be further split. Prediction and transform areboth applied on CU in the same way as JEM. The whole partition structureis named ‘multiple-type-tree’.

2.1.5 Partitioning Structure

The tree structure used in this response, called Multi-Tree Type (MTT),is a generalization of the QTBT. In QTBT, as shown in FIG. 5, a CodingTree Unit (CTU) is firstly partitioned by a quad-tree structure. Thequad-tree leaf nodes are further partitioned by a binary-tree structure.

The fundamental structure of MTT constitutes of two types of tree nodes:Region Tree (RT) and Prediction Tree (PT), supporting nine types ofpartitions, as shown in FIG. 7.

FIG. 7 shows: (a) quad-tree partitioning (b) vertical binary-treepartitioning (c) horizontal binary-tree partitioning (d) verticalternary-tree partitioning (e) horizontal ternary-tree partitioning (f)horizontal-up asymmetric binary-tree partitioning (g) horizontal-downasymmetric binary-tree partitioning (h) vertical-left asymmetricbinary-tree partitioning (i) vertical-right asymmetric binary-treepartitioning.

A region tree can recursively split a CTU into square blocks down to a4×4 size region tree leaf node. At each node in a region tree, aprediction tree can be formed from one of three tree types: Binary Tree(BT), Ternary Tree (TT), and Asymmetric Binary Tree (ABT). In a PTsplit, it is prohibited to have a quadtree partition in branches of theprediction tree. As in JEM, the luma tree and the chroma tree areseparated in I slices. The signaling methods for RT and PT areillustrated in FIG. 8.

2.2 Inter Prediction in HEVC/H.265

Each inter-predicted PU has motion parameters for one or two referencepicture lists. Motion parameters include a motion vector and a referencepicture index. Usage of one of the two reference picture lists may alsobe signalled using inter_pred_idc. Motion vectors may be explicitlycoded as deltas relative to predictors, such a coding mode is calledAMVP mode.

When a CU is coded with skip mode, one PU is associated with the CU, andthere are no significant residual coefficients, no coded motion vectordelta or reference picture index. A merge mode is specified whereby themotion parameters for the current PU are obtained from neighbouring PUs,including spatial and temporal candidates. The merge mode can be appliedto any inter-predicted PU, not only for skip mode. The alternative tomerge mode is the explicit transmission of motion parameters, wheremotion vector, corresponding reference picture index for each referencepicture list and reference picture list usage are signalled explicitlyper each PU.

When signalling indicates that one of the two reference picture lists isto be used, the PU is produced from one block of samples. This isreferred to as ‘uni-prediction’. Uni-prediction is available both forP-slices and B-slices.

When signalling indicates that both of the reference picture lists areto be used, the PU is produced from two blocks of samples. This isreferred to as ‘bi-prediction’. Bi-prediction is available for B-slicesonly.

The following text provides the details on the inter prediction modesspecified in HEVC. The description will start with the merge mode.

2.2.1 Merge Mode

2.2.1.1 Derivation of Candidates for Merge Mode

When a PU is predicted using merge mode, an index pointing to an entryin the merge candidates list is parsed from the bitstream and used toretrieve the motion information. The construction of this list isspecified in the HEVC standard and can be summarized according to thefollowing sequence of steps:

-   -   Step 1: Initial candidates derivation        -   Step 1.1: Spatial candidates derivation        -   Step 1.2: Redundancy check for spatial candidates        -   Step 1.3: Temporal candidates derivation    -   Step 2: Additional candidates insertion        -   Step 2.1: Creation of bi-predictive candidates        -   Step 2.2: Insertion of zero motion candidates

These steps are also schematically depicted in FIG. 9. For spatial mergecandidate derivation, a maximum of four merge candidates are selectedamong candidates that are located in five different positions. Fortemporal merge candidate derivation, a maximum of one merge candidate isselected among two candidates. Since constant number of candidates foreach PU is assumed at decoder, additional candidates are generated whenthe number of candidates does not reach to maximum number of mergecandidate (MaxNumMergeCand) which is signalled in slice header. Sincethe number of candidates is constant, index of best merge candidate isencoded using truncated unary binarization (TU). If the size of CU isequal to 8, all the PUs of the current CU share a single merge candidatelist, which is identical to the merge candidate list of the 2Nx2Nprediction unit.

In the following, the operations associated with the aforementionedsteps are detailed.

2.2.1.2 Spatial candidates derivation

In the derivation of spatial merge candidates, a maximum of four mergecandidates are selected among candidates located in the positionsdepicted in FIG. 10. The order of derivation is A₁, B₁, B₀, A₀ and B₂.Position B₂ is considered only when any PU of position A₁, B₁, B₀, A₀ isnot available (e.g. because it belongs to another slice or tile) or isintra coded. After candidate at position Ai is added, the addition ofthe remaining candidates is subject to a redundancy check which ensuresthat candidates with same motion information are excluded from the listso that coding efficiency is improved. To reduce computationalcomplexity, not all possible candidate pairs are considered in thementioned redundancy check. Instead only the pairs linked with an arrowin FIG. 11 are considered and a candidate is only added to the list ifthe corresponding candidate used for redundancy check has not the samemotion information. Another source of duplicate motion information isthe “second PU” associated with partitions different from 2Nx2N. As anexample, FIG. 12 depicts the second PU for the case of Nx2N and 2NxN,respectively. When the current PU is partitioned as Nx2N, candidate atposition A_(i) is not considered for list construction. In fact, byadding this candidate will lead to two prediction units having the samemotion information, which is redundant to just have one PU in a codingunit. Similarly, position B₁ is not considered when the current PU ispartitioned as 2NxN.

2.2.1.3 Temporal Candidate Derivation

In this step, only one candidate is added to the list. Particularly, inthe derivation of this temporal merge candidate, a scaled motion vectoris derived based on co-located PU belonging to the picture which has thesmallest POC difference with current picture within the given referencepicture list. The reference picture list to be used for derivation ofthe co-located PU is explicitly signalled in the slice header. Thescaled motion vector for temporal merge candidate is obtained asillustrated by the dashed line in FIG. 13, which is scaled from themotion vector of the co-located PU using the POC distances, tb and td,where tb is defined to be the POC difference between the referencepicture of the current picture and the current picture and td is definedto be the POC difference between the reference picture of the co-locatedpicture and the co-located picture. The reference picture index oftemporal merge candidate is set equal to zero. A practical realizationof the scaling process is described in the HEVC specification. For aB-slice, two motion vectors, one is for reference picture list 0 and theother is for reference picture list 1, are obtained and combined to makethe bi-predictive merge candidate. Illustration of motion vector scalingfor temporal merge candidate.

In the co-located PU (Y) belonging to the reference frame, the positionfor the temporal candidate is selected between candidates C₀ and C₁, asdepicted in FIG. 14. If PU at position C₀ is not available, is intracoded, or is outside of the current CTU, position C₁ is used. Otherwise,position C₀ is used in the derivation of the temporal merge candidate.

2.2.1.4 Additional Candidates Insertion

Besides spatio-temporal merge candidates, there are two additional typesof merge candidates: combined bi-predictive merge candidate and zeromerge candidate. Combined bi-predictive merge candidates are generatedby utilizing spatio-temporal merge candidates. Combined bi-predictivemerge candidate is used for B-Slice only. The combined bi-predictivecandidates are generated by combining the first reference picture listmotion parameters of an initial candidate with the second referencepicture list motion parameters of another. If these two tuples providedifferent motion hypotheses, they will form a new bi-predictivecandidate. As an example, FIG. 15 depicts the case when two candidatesin the original list (on the left), which have mvL0 and refIdxL0 or mvL1and refIdxL1, are used to create a combined bi-predictive mergecandidate added to the final list (on the right). There are numerousrules regarding the combinations which are considered to generate theseadditional merge candidates.

Zero motion candidates are inserted to fill the remaining entries in themerge candidates list and therefore hit the MaxNumMergeCand capacity.These candidates have zero spatial displacement and a reference pictureindex which starts from zero and increases every time a new zero motioncandidate is added to the list. The number of reference frames used bythese candidates is one and two for uni and bi-directional prediction,respectively. Finally, no redundancy check is performed on thesecandidates.

2.2.1.5 Motion Estimation Regions for Parallel Processing

To speed up the encoding process, motion estimation can be performed inparallel whereby the motion vectors for all prediction units inside agiven region are derived simultaneously. The derivation of mergecandidates from spatial neighbourhood may interfere with parallelprocessing as one prediction unit cannot derive the motion parametersfrom an adjacent PU until its associated motion estimation is completed.To mitigate the trade-off between coding efficiency and processinglatency, HEVC defines the motion estimation region (MER) whose size issignalled in the picture parameter set using the“log2_parallel_merge_level_minus2” syntax element. When a MER isdefined, merge candidates falling in the same region are marked asunavailable and therefore not considered in the list construction.

7.3.2.3 Picture Parameter set RBSP Syntax

7.3.2.3.1 General Picture Parameter Set RBSP Syntax

pic_parameter_set_rbsp( ) { Descriptor  pps_pic_parameter_set_id ue(v) pps_seq_parameter_set_id ue(v)  dependent_slice_segments_enabled_flagu(1) ...  pps_scaling_list_data_present_flag u(1)  if(pps_scaling_list_data_present_flag )   scaling_list_data( ) lists_modification_present_flag u(1)  log2_parallel_merge_level_minus2ue(v)  slice_segment_header_extension_present_flag u(1) pps_extension_present_flag u(1) ...  rbsp_trailing_bits( ) }

log2_parallel_merge_level_minus2 plus 2 specifies the value of thevariable Log2ParMrgLevel, which is used in the derivation process forluma motion vectors for merge mode as specified in clause 8.5.3.2.2 andthe derivation process for spatial merging candidates as specified inclause 8.5.3.2.3. The value of log2_parallel_merge_level_minus2 shall bein the range of 0 to CtbLog2SizeY−2, inclusive.

The variable Log2ParMrgLevel is derived as follows:

Log2ParMrgLevel=log2_parallel_merge_level_minus2+2   (7-37)

NOTE 3—The value of Log2ParMrgLevel indicates the built-in capability ofparallel derivation of the merging candidate lists. For example, whenLog2ParMrgLevel is equal to 6, the merging candidate lists for all theprediction units (PUs) and coding units (CUs) contained in a 64×64 blockcan be derived in parallel.

2.2.2 Motion Vector Prediction in AMVP Mode

Motion vector prediction exploits spatio-temporal correlation of motionvector with neighbouring PUs, which is used for explicit transmission ofmotion parameters. It constructs a motion vector candidate list byfirstly checking availability of left, above temporally neighbouring PUpositions, removing redundant candidates and adding zero vector to makethe candidate list to be constant length. Then, the encoder can selectthe best predictor from the candidate list and transmit thecorresponding index indicating the chosen candidate. Similarly withmerge index signalling, the index of the best motion vector candidate isencoded using truncated unary. The maximum value to be encoded in thiscase is 2 (e.g., FIGS. 2 to 8). In the following sections, details aboutderivation process of motion vector prediction candidate are provided.

2.2.2.1 Derivation of Motion Vector Prediction Candidates

FIG. 16 summarizes derivation process for motion vector predictioncandidate.

In motion vector prediction, two types of motion vector candidates areconsidered: spatial motion vector candidate and temporal motion vectorcandidate. For spatial motion vector candidate derivation, two motionvector candidates are eventually derived based on motion vectors of eachPU located in five different positions as depicted in FIG. 11.

For temporal motion vector candidate derivation, one motion vectorcandidate is selected from two candidates, which are derived based ontwo different co-located positions. After the first list ofspatio-temporal candidates is made, duplicated motion vector candidatesin the list are removed. If the number of potential candidates is largerthan two, motion vector candidates whose reference picture index withinthe associated reference picture list is larger than 1 are removed fromthe list. If the number of spatio-temporal motion vector candidates issmaller than two, additional zero motion vector candidates is added tothe list.

2.2.2.2 Spatial Motion vVector Candidates

In the derivation of spatial motion vector candidates, a maximum of twocandidates are considered among five potential candidates, which arederived from PUs located in positions as depicted in FIG. 11, thosepositions being the same as those of motion merge. The order ofderivation for the left side of the current PU is defined as A₀, A₁, andscaled A₀, scaled A₁. The order of derivation for the above side of thecurrent PU is defined as B₀, B₁, B₂, scaled B₀, scaled B₁, scaled B₂.For each side there are therefore four cases that can be used as motionvector candidate, with two cases not required to use spatial scaling,and two cases where spatial scaling is used. The four different casesare summarized as follows.

No Spatial Scaling

-   -   (1) Same reference picture list, and same reference picture        index (same POC)    -   (2) Different reference picture list, but same reference picture        (same POC)

Spatial scaling

-   -   (3) Same reference picture list, but different reference picture        (different POC)    -   (4) Different reference picture list, and different reference        picture (different POC)

The no-spatial-scaling cases are checked first followed by the spatialscaling. Spatial scaling is considered when the POC is different betweenthe reference picture of the neighbouring PU and that of the current PUregardless of reference picture list. If all PUs of left candidates arenot available or are intra coded, scaling for the above motion vector isallowed to help parallel derivation of left and above MV candidates.Otherwise, spatial scaling is not allowed for the above motion vector.

In a spatial scaling process, the motion vector of the neighbouring PUis scaled in a similar manner as for temporal scaling, as depicted asFIG. 17. The main difference is that the reference picture list andindex of current PU is given as input; the actual scaling process is thesame as that of temporal scaling.

2.2.2.3 Temporal motion vector candidates

Apart for the reference picture index derivation, all processes for thederivation of temporal merge candidates are the same as for thederivation of spatial motion vector candidates (see, e.g., FIG. 6). Thereference picture index is signalled to the decoder.

2.2.2.4 Signaling of AMVP Information

For the AMVP mode, four parts may be signalled in the bitstream, i.e.,prediction direction, reference index, MVD and my predictor candidateindex.

Syntax tables:

De- prediction_unit( x0, y0, nPbW, nPbH ) { scriptor  if( cu_skip_flag[x0 ][ y0 ]) {   if( MaxNumMergeCand > 1 )    merge_idx[ x0 ][ y0 ] ae(v) } else { /* MODE_INTER */   merge_flag[ x0 ][ y0 ] ae(v)   if(merge_flag[ x0 ][ y0 ] ) {    if( MaxNumMergeCand > 1 )     merge_idx[x0 ][ y0 ] ae(v)   } else {    if( slice_type = = B)     inter_pred_idc[x0 ][ y0 ] ae(v)    if( inter_pred_idc[ x0 ][ y0 ] != PRED_L1 ) {    if( num_ref_ idx_10_active_minus1 > 0 )      ref_ idx_l0[ x0 ][ y0 ]ae(v)     mvd_coding( x0, y0, 0 )     mvp_l0 flag[ x0 ][ y0 ] ae(v)    }   if( inter_pred_idc[ x0 ][ y0 ] != PRED_L0 ) {     if(num_ref_idx_l1_active_minus1 > 0 )      ref_idx_l1[ x0 ][ y0 ] ae(v)    if( mvd_l1_zero_flag && inter_pred_idc[ x0 ][ y0 ] = = PRED_ BI ) {     MvdL1[ x0 ][ y0 ][ 0 ] = 0      MvdL1[ x0 ][ y0 ][ 1 ] = 0     }else      mvd_coding( x0, y0, 1 )     mvp_l1_flag[ x0 ][ y0 ] ae(v)    }  }  } }

7.3.8.9 Motion Vector Difference Syntax

mvd_coding( x0, y0, refList ) { Descriptor  abs_mvd_greater0_flag[ 0 ]ae(v)  abs_mvd_greater0_flag[ 1 ] ae(v)  if( abs_mvd_greater0_flag[ 0 ])   abs_mvd_greater1_flag[ 0 ] ae(v)  if( abs_mvd_greater0_flag[ 1 ] )  abs_mvd_greater1_flag[ 1 ] ae(v)  if( abs_mvd_greater0_flag[ 0 ] ) {  if( abs_mvd_greater1_flag[ 0 ] )    abs_mvd_minus2[ 0 ] ae(v)  mvd_sign_flag[ 0 ] ae(v)  }  if( abs_mvd_greater0_flag[ 1 ] ) {   if(abs_mvd_greater1_flag[ 1 ] )    abs_mvd_minus2[ 1 ] ae(v)  mvd_sign_flag[ 1 ] ae(v)  } }

2.3 New Inter Prediction Methods in JEM (Joint Exploration Model)

2.3.1 Sub-CU Based Motion Vector Prediction

In the JEM with QTBT, each CU can have at most one set of motionparameters for each prediction direction. Two sub-CU level motion vectorprediction methods are considered in the encoder by splitting a large CUinto sub-CUs and deriving motion information for all the sub-CUs of thelarge CU. Alternative temporal motion vector prediction (ATMVP) methodallows each CU to fetch multiple sets of motion information frommultiple blocks smaller than the current CU in the collocated referencepicture. In spatial-temporal motion vector prediction (STMVP) methodmotion vectors of the sub-CUs are derived recursively by using thetemporal motion vector predictor and spatial neighbouring motion vector.

To preserve more accurate motion field for sub-CU motion prediction, themotion compression for the reference frames is currently disabled.

2.3.1.1 Alternative Temporal Motion Vector Prediction

In the alternative temporal motion vector prediction (ATMVP) method, themotion vectors temporal motion vector prediction (TMVP) is modified byfetching multiple sets of motion information (including motion vectorsand reference indices) from blocks smaller than the current CU. As shownin FIG. 18, the sub-CUs are square NxN blocks (N is set to 4 bydefault).

ATMVP predicts the motion vectors of the sub-CUs within a CU in twosteps. The first step is to identify the corresponding block in areference picture with a so-called temporal vector. The referencepicture is called the motion source picture. The second step is to splitthe current CU into sub-CUs and obtain the motion vectors as well as thereference indices of each sub-CU from the block corresponding to eachsub-CU, as shown in FIG. 18.

In the first step, a reference picture and the corresponding block isdetermined by the motion information of the spatial neighbouring blocksof the current CU. To avoid the repetitive scanning process ofneighbouring blocks, the first merge candidate in the merge candidatelist of the current CU is used. The first available motion vector aswell as its associated reference index are set to be the temporal vectorand the index to the motion source picture. This way, in ATMVP, thecorresponding block may be more accurately identified, compared withTMVP, wherein the corresponding block (sometimes called collocatedblock) is always in a bottom-right or center position relative to thecurrent CU. In one example, if the first merge candidate is from theleft neighboring block (i.e., Ai in FIG. 19), the associated MV andreference picture are utilized to identify the source block and sourcepicture.

FIG. 19 shows an example of the identification of source block andsource picture

In the second step, a corresponding block of the sub-CU is identified bythe temporal vector in the motion source picture, by adding to thecoordinate of the current CU the temporal vector. For each sub-CU, themotion information of its corresponding block (the smallest motion gridthat covers the center sample) is used to derive the motion informationfor the sub-CU. After the motion information of a corresponding NxNblock is identified, it is converted to the motion vectors and referenceindices of the current sub-CU, in the same way as TMVP of HEVC, whereinmotion scaling and other procedures apply. For example, the decoderchecks whether the low-delay condition (i.e. the POCs of all referencepictures of the current picture are smaller than the POC of the currentpicture) is fulfilled and possibly uses motion vector MV_(x) (the motionvector corresponding to reference picture list X) to predict motionvector MV_(y) (with X being equal to 0 or 1 and Y being equal to 1−X)for each sub-CU.

2.3.1.2 Spatial-Temporal Motion Vector Prediction

In this method, the motion vectors of the sub-CUs are derivedrecursively, following raster scan order. FIG. 20 illustrates thisconcept. Let us consider an 8×8 CU which contains four 4×4 sub-CUs A, B,C, and D. The neighbouring 4×4 blocks in the current frame are labelledas a, b, c, and d.

The motion derivation for sub-CU A starts by identifying its two spatialneighbours. The first neighbour is the NxN block above sub-CU A (blockc). If this block c is not available or is intra coded the other NxNblocks above sub-CU A are checked (from left to right, starting at blockc). The second neighbour is a block to the left of the sub-CU A (blockb). If block b is not available or is intra coded other blocks to theleft of sub-CU A are checked (from top to bottom, staring at block b).The motion information obtained from the neighbouring blocks for eachlist is scaled to the first reference frame for a given list. Next,temporal motion vector predictor (TMVP) of sub-block A is derived byfollowing the same procedure of TMVP derivation as specified in HEVC.The motion information of the collocated block at location D is fetchedand scaled accordingly. Finally, after retrieving and scaling the motioninformation, all available motion vectors (up to 3) are averagedseparately for each reference list. The averaged motion vector isassigned as the motion vector of the current sub-CU.

FIG. 20 shows an example of one CU with four sub-blocks (A-D) and itsneighbouring blocks (a-d).

2.3.1.3 Sub-CU Motion Prediction Mode Signalling

The sub-CU modes are enabled as additional merge candidates and there isno additional syntax element required to signal the modes. Twoadditional merge candidates are added to merge candidates list of eachCU to represent the ATMVP mode and STMVP mode. Up to seven mergecandidates are used, if the sequence parameter set indicates that ATMVPand STMVP are enabled. The encoding logic of the additional mergecandidates is the same as for the merge candidates in the HM, whichmeans, for each CU in P or B slice, two more RD checks is needed for thetwo additional merge candidates.

In the JEM, all bins of merge index is context coded by CABAC. While inHEVC, only the first bin is context coded and the remaining bins arecontext by-pass coded.

2.3.2 Adaptive Motion Vector Difference Resolution

In HEVC, motion vector differences (MVDs) (between the motion vector andpredicted motion vector of a PU) are signalled in units of quarter lumasamples when use_integer_mv_flag is equal to 0 in the slice header. Inthe JEM, a locally adaptive motion vector resolution (LAMVR) isintroduced. In the JEM, MVD can be coded in units of quarter lumasamples, integer luma samples or four luma samples. The MVD resolutionis controlled at the coding unit (CU) level, and MVD resolution flagsare conditionally signalled for each CU that has at least one non-zeroMVD components.

For a CU that has at least one non-zero MVD components, a first flag issignalled to indicate whether quarter luma sample MV precision is usedin the CU. When the first flag (equal to 1) indicates that quarter lumasample MV precision is not used, another flag is signalled to indicatewhether integer luma sample MV precision or four luma sample MVprecision is used.

When the first MVD resolution flag of a CU is zero, or not coded for aCU (meaning all MVDs in the CU are zero), the quarter luma sample MVresolution is used for the CU. When a CU uses integer-luma sample MVprecision or four-luma-sample MV precision, the MVPs in the AMVPcandidate list for the CU are rounded to the corresponding precision.

In the encoder, CU-level RD checks are used to determine which MVDresolution is to be used for a CU. That is, the CU-level RD check isperformed three times for each MVD resolution. To accelerate encoderspeed, the following encoding schemes are applied in the JEM.

During RD check of a CU with normal quarter luma sample MVD resolution,the motion information of the current CU (integer luma sample accuracy)is stored. The stored motion information (after rounding) is used as thestarting point for further small range motion vector refinement duringthe RD check for the same CU with integer luma sample and 4 luma sampleMVD resolution so that the time-consuming motion estimation process isnot duplicated three times.

RD check of a CU with 4 luma sample MVD resolution is conditionallyinvoked. For a CU, when RD cost integer luma sample MVD resolution ismuch larger than that of quarter luma sample MVD resolution, the RDcheck of 4 luma sample MVD resolution for the CU is skipped.

2.3.3 Pattern Matched Motion Vector Derivation

Pattern matched motion vector derivation (PMMVD) mode is a special mergemode based on Frame-Rate Up Conversion (FRUC) techniques. With thismode, motion information of a block is not signalled but derived atdecoder side.

A FRUC flag is signalled for a CU when its merge flag is true. When theFRUC flag is false, a merge index is signalled and the regular mergemode is used. When the FRUC flag is true, an additional FRUC mode flagis signalled to indicate which method (bilateral matching or templatematching) is to be used to derive motion information for the block.

At encoder side, the decision on whether using FRUC merge mode for a CUis based on RD cost selection as done for normal merge candidate. Thatis the two matching modes (bilateral matching and template matching) areboth checked for a CU by using RD cost selection. The one leading to theminimal cost is further compared to other CU modes. If a FRUC matchingmode is the most efficient one, FRUC flag is set to true for the CU andthe related matching mode is used.

Motion derivation process in FRUC merge mode has two steps. A CU-levelmotion search is first performed, then followed by a Sub-CU level motionrefinement. At CU level, an initial motion vector is derived for thewhole CU based on bilateral matching or template matching. First, a listof MV candidates is generated and the candidate which leads to theminimum matching cost is selected as the starting point for further CUlevel refinement. Then a local search based on bilateral matching ortemplate matching around the starting point is performed and the MVresults in the minimum matching cost is taken as the MV for the wholeCU. Subsequently, the motion information is further refined at sub-CUlevel with the derived CU motion vectors as the starting points.

For example, the following derivation process is performed for a W×H CUmotion information derivation. At the first stage, MV for the whole W×HCU is derived. At the second stage, the CU is further split into M×Msub-CUs. The value of M is calculated as in (16), D is a predefinedsplitting depth which is set to 3 by default in the JEM. Then the MV foreach sub-CU is derived.

$\begin{matrix}{M = {\max\left\{ {4,{\min\left\{ {\frac{M}{2^{D}},\ \frac{N}{2^{D}}} \right\}}} \right\}}} & (1)\end{matrix}$

As shown in the FIG. 21, the bilateral matching is used to derive motioninformation of the current CU by finding the closest match between twoblocks along the motion trajectory of the current CU in two differentreference pictures. Under the assumption of continuous motiontrajectory, the motion vectors MV0 and MV1 pointing to the two referenceblocks shall be proportional to the temporal distances, i.e., TD0 andTD1, between the current picture and the two reference pictures. As aspecial case, when the current picture is temporally between the tworeference pictures and the temporal distance from the current picture tothe two reference pictures is the same, the bilateral matching becomesmirror based bi-directional MV.

As shown in FIG. 22, template matching is used to derive motioninformation of the current CU by finding the closest match between atemplate (top and/or left neighbouring blocks of the current CU) in thecurrent picture and a block (same size to the template) in a referencepicture. Except the aforementioned FRUC merge mode, the templatematching is also applied to AMVP mode. In the JEM, as done in HEVC, AMVPhas two candidates. With template matching method, a new candidate isderived. If the newly derived candidate by template matching isdifferent to the first existing AMVP candidate, it is inserted at thevery beginning of the AMVP candidate list and then the list size is setto two (meaning remove the second existing AMVP candidate). When appliedto AMVP mode, only CU level search is applied.

2.3.3.1 CU Level MV Candidate Set

The MV candidate set at CU level consists of:

(i) Original AMVP candidates if the current CU is in AMVP mode

(ii) all merge candidates,

(iii) several MVs in the interpolated MV field.

(iv) top and left neighbouring motion vectors

When using bilateral matching, each valid MV of a merge candidate isused as an input to generate a MV pair with the assumption of bilateralmatching. For example, one valid MV of a merge candidate is (MVa, refa)at reference list A. Then the reference picture refb of its pairedbilateral MV is found in the other reference list B so that refa andrefb are temporally at different sides of the current picture. If such arefb is not available in reference list B, refb is determined as areference which is different from refa and its temporal distance to thecurrent picture is the minimal one in list B. After refb is determined,MVb is derived by scaling MVa based on the temporal distance between thecurrent picture and refa, refb.

Four MVs from the interpolated MV field are also added to the CU levelcandidate list. More specifically, the interpolated MVs at the position(0, 0), (W/2, 0), (0, H/2) and (W/2, H/2) of the current CU are added.

When FRUC is applied in AMVP mode, the original AMVP candidates are alsoadded to CU level MV candidate set.

At the CU level, up to 15 MVs for AMVP CUs and up to 13 MVs for mergeCUs are added to the candidate list.

2.3.3.2 Sub-CU Level MV Candidate Set

The MV candidate set at sub-CU level consists of:

(i) an MV determined from a CU-level search,

(ii) top, left, top-left and top-right neighbouring MVs,

(iii) scaled versions of collocated MVs from reference pictures,

(iv) up to 4 ATMVP candidates,

(v) up to 4 STMVP candidates

The scaled MVs from reference pictures are derived as follows. All thereference pictures in both lists are traversed. The MVs at a collocatedposition of the sub-CU in a reference picture are scaled to thereference of the starting CU-level MV.

ATMVP and STMVP candidates are limited to the four first ones.

At the sub-CU level, up to 17 MVs are added to the candidate list.

2.3.3.3 Generation of Interpolated MV Field

Before coding a frame, interpolated motion field is generated for thewhole picture based on unilateral ME. Then the motion field may be usedlater as CU level or sub-CU level MV candidates.

First, the motion field of each reference pictures in both referencelists is traversed at 4×4 block level. For each 4×4 block, if the motionassociated to the block passing through a 4×4 block in the currentpicture (as shown in FIG. 23) and the block has not been assigned anyinterpolated motion, the motion of the reference block is scaled to thecurrent picture according to the temporal distance TDO and TD1 (the sameway as that of MV scaling of TMVP in HEVC) and the scaled motion isassigned to the block in the current frame. If no scaled MV is assignedto a 4×4 block, the block's motion is marked as unavailable in theinterpolated motion field.

2.3.3.4 Interpolation and Matching Cost

When a motion vector points to a fractional sample position, motioncompensated interpolation is needed. To reduce complexity, bi-linearinterpolation instead of regular 8-tap HEVC interpolation is used forboth bilateral matching and template matching.

The calculation of matching cost is a bit different at different steps.When selecting the candidate from the candidate set at the CU level, thematching cost is the absolute sum difference (SAD) of bilateral matchingor template matching. After the starting MV is determined, the matchingcost C of bilateral matching at sub-CU level search is calculated asfollows:

C=SAD+w·(|MV _(x) −MV _(x) ^(s) |+|MV _(y) −MV _(y) ^(s)|)   (2)

where w is a weighting factor which is empirically set to 4, MV and MVSindicate the current MV and the starting MV, respectively. SAD is stillused as the matching cost of template matching at sub-CU level search.

In FRUC mode, MV is derived by using luma samples only. The derivedmotion will be used for both luma and chroma for MC inter prediction.After MV is decided, final MC is performed using 8-taps interpolationfilter for luma and 4-taps interpolation filter for chroma.

2.3.3.5 MV Refinement

MV refinement is a pattern based MV search with the criterion ofbilateral matching cost or template matching cost. In the JEM, twosearch patterns are supported—an unrestricted center-biased diamondsearch (UCBDS) and an adaptive cross search for MV refinement at the CUlevel and sub-CU level, respectively. For both CU and sub-CU level MVrefinement, the MV is directly searched at quarter luma sample MVaccuracy, and this is followed by one-eighth luma sample MV refinement.The search range of MV refinement for the CU and sub-CU step are setequal to 8 luma samples.

2.3.3.6 Selection of Prediction Direction in Template Matching FRUCMerge Mode

In the bilateral matching merge mode, bi-prediction is always appliedsince the motion information of a CU is derived based on the closestmatch between two blocks along the motion trajectory of the current CUin two different reference pictures. There is no such limitation for thetemplate matching merge mode. In the template matching merge mode, theencoder can choose among uni-prediction from list0, uni-prediction fromlistl or bi-prediction for a CU. The selection is based on a templatematching cost as follows:

If costBi<=factor*min (cost0, cost1)

bi-prediction is used;

Otherwise, if cost0<=cost1

uni-prediction from list0 is used;

Otherwise,

uni-prediction from listl is used;

where cost0 is the SAD of list0 template matching, costl is the SAD oflistl template matching and costBi is the SAD of bi-prediction templatematching. The value of factor is equal to 1.25, which means that theselection process is biased toward bi-prediction. The inter predictiondirection selection is only applied to the CU-level template matchingprocess.

2.3.4 Decoder-side motion vector refinement

In bi-prediction operation, for the prediction of one block region, twoprediction blocks, formed using a motion vector (MV) of list0 and a MVof list1, respectively, are combined to form a single prediction signal.In the decoder-side motion vector refinement (DMVR) method, the twomotion vectors of the bi-prediction are further refined by a bilateraltemplate matching process. The bilateral template matching applied inthe decoder to perform a distortion-based search between a bilateraltemplate and the reconstruction samples in the reference pictures inorder to obtain a refined MV without transmission of additional motioninformation.

In DMVR, a bilateral template is generated as the weighted combination(i.e. average) of the two prediction blocks, from the initial MVO oflist0 and MV1 of listl, respectively, as shown in FIG. 23. The templatematching operation consists of calculating cost measures between thegenerated template and the sample region (around the initial predictionblock) in the reference picture. For each of the two reference pictures,the MV that yields the minimum template cost is considered as theupdated MV of that list to replace the original one. In the JEM, nine MVcandidates are searched for each list. The nine MV candidates includethe original MV and 8 surrounding MVs with one luma sample offset to theoriginal MV in either the horizontal or vertical direction, or both.Finally, the two new MVs, i.e., MV0′ and MV1′ as shown in FIG. 24, areused for generating the final bi-prediction results. A sum of absolutedifferences (SAD) is used as the cost measure.

DMVR is applied for the merge mode of bi-prediction with one MV from areference picture in the past and another from a reference picture inthe future, without the transmission of additional syntax elements. Inthe JEM, when LIC, affine motion, FRUC, or sub-CU merge candidate isenabled for a CU, DMVR is not applied.

2.3.5 Merge/Skip Mode with Bilateral Matching Refinement

A merge candidate list is first constructed by inserting the motionvectors and reference indices of the spatial neighboring and temporalneighboring blocks into the candidate list with redundancy checkinguntil the number of the available candidates reaches the maximumcandidate size of 19. The merge candidate list for the merge/skip modeis constructed by inserting spatial candidates (FIG. 11), temporalcandidates, affine candidates, advanced temporal MVP (ATMVP) candidate,spatial temporal MVP (STMVP) candidate and the additional candidates asused in HEVC (Combined candidates and Zero candidates) according to apre-defined insertion order:

Spatial candidates for blocks 1-4.

Extrapolated affine candidates for blocks 1-4.

ATMVP.

STMVP.

Virtual affine candidate.

Spatial candidate (block 5) (used only when the number of the availablecandidates is smaller than 6).

Extrapolated affine candidate (block 5).

Temporal candidate (derived as in HEVC).

Non-adjacent spatial candidates followed by extrapolated affinecandidate (blocks 6 to 49, as depicted in FIG. 25).

Combined candidates.

Zero candidates

It is noted that IC flags are also inherited from merge candidatesexcept for STMVP and affine. Moreover, for the first four spatialcandidates, the bi-prediction ones are inserted before the ones withuni-prediction.

Blocks which are not connected with the current block may be accessed.If a non-adjacent block is coded with non-intra mode, the associatedmotion information may be added as an additional merge candidate.

2.3.6 Shared Merge List JVET-M0170

It proposes to share the same merging candidate list for all leaf codingunits (CUs) of one ancestor node in the CU split tree for enablingparallel processing of small skip/merge-coded CUs. The ancestor node isnamed merge sharing node. The shared merging candidate list is generatedat the merge sharing node pretending the merge sharing node is a leafCU.

For Type-2 definition, the merge sharing node will be decided for eachCU inside a CTU during parsing stage of decoding; moreover, the mergesharing node is an ancestor node of leaf CU which must satisfy thefollowing 2 criteria:

The merge sharing node size is equal to or larger than the sizethreshold

In the merge sharing node, one of the child CU size is smaller than thesize threshold

Moreover, no samples of the merge sharing node are outside the pictureboundary has to be guaranteed. During parsing stage, if an ancestor nodesatisfies the criteria (1) and (2) but has some samples outside thepicture boundary, this ancestor node will not be the merge sharing nodeand it proceeds to find the merge sharing node for its child CUs.

FIG. 35 shows an example for the difference of Type-1 and Type-2definition. In this example, the parent node is ternary-split into 3child CUs. The size of parent node is 128. For Type-1 definition, the 3child-CUs will be merge sharing nodes separately. But for Type-2definition, the parent node is the merge sharing node.

The proposed shared merging candidate list algorithm supportstranslational merge (including merge mode and triangle merge mode,history-based candidate is also supported) and subblock-based mergemode. For all kinds of merge mode, the behavior of shared mergingcandidate list algorithm looks basically the same, and it just generatescandidates at the merge sharing node pretending the merge sharing nodeis a leaf CU. It has 2 major benefits. The first benefit is to enableparallel processing for merge mode, and the second benefit is to shareall computations of all leaf CUs into the merge sharing node. Therefore,it significantly reduces the hardware cost of all merge modes forhardware codec. By the proposed shared merging candidate list algorithm,the encoder and decoder can easily support parallel encoding for mergemode and it relieves the cycle budget problem of merge mode.

2.3.7 Tile Groups

JVET-L0686 was adopted in which slices are removed in favor of tilegroups and the HEVC syntax element slice_address is substituted withtile_group address in the tile_group_header (if there is more than onetile in the picture) as address of the first tile in the tile group.

3. Examples of Problems Addressed by Embodiments Disclosed Herein

The current HEVC design could take the correlation of current block itsneighbouring blocks (next to the current block) to better code themotion information. However, it is possible that that the neighbouringblocks correspond to different objects with different motiontrajectories. In this case, prediction from its neighbouring blocks isnot efficient.

Prediction from motion information of non-adjacent blocks could bringadditional coding gain with the cost of storing all the motioninformation (typically on 4×4 level) into cache which significantlyincrease the complexity for hardware implementation.

4. Some Examples

The examples below should be considered as examples to explain generalconcepts. These examples should not be interpreted in a narrow way.Furthermore, these examples can be combined in any manner.

Some embodiments may use one or more look up tables with at least onemotion candidate stored to predict motion information of a block.Embodiments may use motion candidate to indicate a set of motioninformation stored in a look up table. For conventional AMVP or mergemodes, embodiments may use AMVP or merge candidates for storing themotion information.

The examples below explain general concepts.

Examples of look-up tables

Example A1: Each look up table may contain one or more motion candidateswherein each candidate is associated with its motion information.

-   -   a. Motion information of a motion candidate here may include        partial or all of the prediction direction, reference        indices/pictures, motion vectors, LIC flag, affine flag, MVD        precision, MVD values.    -   b. Motion information may further include the block position        information and/or block shape to indicate wherein the motion        information is coming from.    -   c. A counter may be further assigned for each look up table.        -   i. The counter may be initialized to be zero at the            beginning of encoding/decoding a picture/slice/LCU(CTU)            row/tile.        -   ii. In one example, the counter may be updated after            encoding/decoding a CTU/CTB/CU/CB/PU/a certain region size            (e.g., 8×8 or 16×16).        -   iii. In one example, the counter is increased by one each            time one candidate is added into the lookup table.        -   iv. In one example, the counter should be no larger than the            table size (number of allowed motion candidates).        -   v. Alternatively, the counter may be used to indicate how            many motion candidates have been tried to be added to the            look up tables (some of them was in the look up table but            later may be removed from the table). In this case, the            counter could be larger than the table size.    -   d. The table size (number of allowed motion candidates) and/or        number of tables may be the fixed or adaptive. The table size        may be same for all tables, or different for different tables.        -   i. Alternatively, different sizes may be used for different            look-up tables (e.g., 1 or 2).        -   ii. In one example, the table sizes and/or number of tables            may be pre-defined.        -   iii. In one example, the table sizes and/or number of tables            may be signalled in Video Parameter Set (VPS), Sequence            Parameter Set (SPS), Picture Parameter Set (PPS), Slice            header, tile header, Coding Tree Unit (CTU), Coding Tree            Block (CTB), Coding Unit (CU) or Prediction Unit (PU),            region covering multiple CTU/CTB/CU/PUs.        -   iv. The table size and/or number of tables may further            depend on the slice type, temporal layer index of a picture,            picture order count (POC) distance between one slice and the            closest intra slice.    -   e. Suppose there are N tables used for a coding thread, N*P        tables may be required for coding a slice, wherein P indicates        the number of LCU rows or the number of tiles.        -   i. Alternatively, only P tables may be required for coding a            slice, wherein P indicates the number of LCU rows wherein            each LCU row only use one look up table even N could be            larger than 1 when tile is disabled.

Selection of LUTs

Example B 1: For coding a block, partial or all of motion candidatesfrom one look up table may be checked in order. When one motioncandidate is checked during coding a block, it may be added to themotion candidate list (e.g., AMVP, merge candidate lists).

-   -   a. Alternatively, motion candidates from multiple look up tables        may be checked in order.    -   b. The look up table indices may be signaled in CTU, CTB, CU or        PU, or a region covering multiple CTU/CTB/CU/PUs.

Example B2: The selection of look up tables may depend on the positionof a block.

-   -   a. It may depend on the CTU address covering the block. Here, we        take two look up tables (Dual Look Up Tables, DLUT) for an        example to illustrate the idea:        -   i. If the block is located at one of the first M CTUs in a            CTU row, the first look up table may be utilized for coding            the block, while for blocks located in the remaining CTUs in            the CTU row, the second look up table may be utilized.        -   ii. If the block is located at one of the first M CTUs in a            CTU row, motion candidates of the first look up table may            firstly checked for coding the block, if there are not            enough candidates in the first table, the second look up            table may be further utilized. while for blocks located in            the remaining CTUs in the CTU row, the second look up table            may be utilized.        -   iii. Alternatively, for blocks located in the remaining CTUs            in the CTU row, motion candidates of the second look up            table may firstly checked for coding the block, if there are            not enough candidates in the second table, the first look up            table may be further utilized.    -   b. It may depend on the distance between the position of the        block and the position associated with one motion candidate in        one or multiple look up tables.        -   iv. In one example, if one motion candidate is associated            with a smaller distance to the block to be coded, it may be            checked earlier compared to another motion candidate.

Usage of Look Up Tables

Example C1: The total number of motion candidates in a look up table tobe checked may be pre-defined.

-   -   a. It may further depend on the coded information, block size,        block shape and etc. al. For example, for the AMVP mode, only in        motion candidates may be checked while for the merge mode, n        motion candidates may be checked (e.g., m=2, n =44).    -   b. In one example, the total number of motion candidates to be        checked may be signalled in Video Parameter Set (VPS), Sequence        Parameter Set (SPS), Picture Parameter Set (PPS), Slice header,        tile header, Coding Tree Unit (CTU), Coding Tree Block (CTB),        Coding Unit (CU) or Prediction Unit (PU), region covering        multiple CTU/CTB/CU/PUs.

Example C2: The motion candidate(s) included in a look up table may bedirectly inherited by a block.

-   -   a. They may be used for the merge mode coding, i.e., motion        candidates may be checked in the merge candidate list derivation        process.    -   b. They may be used for the affine merge mode coding.        -   i. A motion candidate in a look up table can be added as an            affine merge candidate if its affine flag is one.    -   c. Checking of motion candidates in look up tables may be        enabled when:        -   i. the merge candidate list is not full after inserting the            TMVP candidate;        -   ii. the merge candidate list is not full after checking a            certain spatial neighboring block for spatial merge            candidate derivation;        -   iii. the merge candidate list is not full after all spatial            merge candidates;        -   iv. the merge candidate list is not full after combined            bi-predictive merge candidates;        -   v. when the number of spatial or temporal (e.g., including            adjacent spatial and non-adjacent spatial, TMVP, STMVP,            ATMVP, etc. al) merge candidates that have been put into the            merge candidate list from other coding methods (e.g., the            merge derivation process of HEVC design, or JEM design) is            less than the maximumly allowed merge candidates minus a            given threshold.            -   1. in one example, the threshold is set to 1 or 0.            -   2. Alternatively, the threshold may be signaled or                pre-defined in SPS/PPS/sequence, picture, slice                header/tile.            -   3. Alternatively, the threshold may be adaptively                changed from block to block. For example, it may be                dependent on coded block information, like block                size/block shape/slice type, and/or dependent on the                number of available spatial or temporal merge                candidates.            -   4. In another example, when the number of a certain kind                of merge candidates than have been put into the merge                candidate list is less than the maximumly allowed merge                candidates minus a given threshold. The “certain kind of                merge candidates” may be spatial candidates as in HEVC                or non-adjacent merge candidates.        -   vi. Pruning may be applied before adding a motion candidate            to the merge candidate list.            -   1. In one example, a motion candidate may be pruned to                all or partial of the available spatial or temporal                (e.g., including adjacent spatial and non-adjacent                spatial, TMVP, STMVP, ATMVP, etc. al) merge candidates                from other coding methods in the merge candidate list.            -   2. a motion candidate may be NOT pruned to sub-block                based motion candidates, e.g., ATMVP, STMVP.            -   3. In one example, a current motion candidate may be                pruned to all or partial of the available motion                candidates (inserted before the current motion                candidate) in the merge candidate list.            -   4. Number of pruning operations related to motion                candidates (that is, how many times that motion                candidates need to be compared to other candidates in                the merge list) may depend on the number of available                spatial or temporal merge candidates. For example, when                checking a new motion candidate, if there are M                candidates available in the merge list, the new motion                candidate may be only compared to the first K (K<=M)                candidates. If the pruning function returns false (e.g.,                not identical to any of the first K candidates), the new                motion candidate is considered to be different from all                of the M candidates and it could be added to the merge                candidate list. In one example, K is set to min (K, 2).            -   5. In one example, a newly appended motion candidate is                only compared with the first N candidate in the merge                candidate list. For example, N=3, 4 or 5. N may be                signaled from the encoder to the decoder.            -   6. In one example, a new motion candidate to be checked                is only compared with the last N candidate in the merge                candidate list. For example, N=3, 4 or 5. N may be                signaled from the encoder to the decoder.            -   7. In one example, how to select candidates previously                added in the list to be compared with a new motion                candidate from a table may depend on where the                previously added candidates derived from.                -   a. In one example, a motion candidate in a look-up                    table may be compared to candidates derived from a                    given temporal and/or spatial neighboring block.                -   b. In one example, different entries of motion                    candidates in a look-up table may be compared to                    different previously added candidates (i.e., derived                    from different locations).

Example C3: The motion candidate(s) included in a look up table may beused as a predictor for coding motion information of a block.

-   -   a. They may be used for the AMVP mode coding, i.e., motion        candidates may be checked in the AMVP candidate list derivation        process.    -   b. Checking of motion candidates in look up tables may be        enabled when:        -   i. the AMVP candidate list is not full after inserting the            TMVP candidate;        -   ii. the AMVP candidate list is not full after selecting from            spatial neighbors and pruning, right before inserting the            TMVP candidate;        -   iii. when there is no AMVP candidate from above neighboring            blocks without scaling and/or when there is no AMVP            candidate from left neighboring blocks without scaling        -   iv. Pruning may be applied before adding a motion candidate            to the AMVP candidate list.        -   v. Similar rules as mentioned in bullet 5.(3) (4) may be            applied to AMVP mode    -   c. Motion candidates with identical reference picture to the        current reference picture is checked.        -   i. Alternatively, in addition, motion candidates with            different reference pictures from the current reference            picture are also checked (with MV scaled).        -   ii. Alternatively, all motion candidates with identical            reference picture to the current reference picture are first            checked, then, motion candidates with different reference            pictures from the current reference picture are checked.        -   iii. Alternatively, motion candidates are checked following            the same in merge.

Example C4: The checking order of motion candidates in a look up tableis defined as follows (suppose K (K>=1) motion candidates are allowed tobe checked):

-   -   a. The last K motion candidates in the look up table, e.g., in        descending order of entry indices to the LUT.    -   b. The first K%L candidates wherein L is the look up table size        when K>=L, e.g., in descending order of entry indices to the        LUT.    -   c. All the candidates (L candidates) in the look up table when        K>=L, based on an order. In one example, the first K%L        candidates in the table are checked in descending order of entry        indices to the LUT, and then check the last (L−K%L) candidates        in descending order of entry indices.    -   d. Alternatively, furthermore, based on the descending order of        motion candidate indices.    -   e. Alternatively, furthermore, based on the ascending order of        motion candidate indices    -   f. Alternatively, selecting K motion candidates based on the        candidate information, such as the distance of positions        associated with the motion candidates and current block.        -   i. In one example, K nearest motion candidates are selected.        -   ii. in one example, the candidate information may further            consider block shape when calculating the distance    -   g. In one example, the checking order of K of motion candidates        from the table which includes L candidates may be defined as:        selecting those candidates with index equal to a₀, a₀+T₀,        a₀+T₀+T₁+T₂, a₀+T₀+a₀+T₀+T₁+T₂+. . . +T_(k−1) in order wherein        a₀ and T_(i) (i being 0 . . . K−1) are integer values.        -   i. In one example, ao is set to 0 (i.e., the first entry of            motion candidate in the table). Alternatively, ao is set to            (K−L/K). The arithmetic operation ‘/’ is defined as integer            division with truncation of the result toward zero.            Alternatively, ao is set to any integer between 0 and L/K.        -   i. Alternatively, the value of a₀ may depend on coding            information of the current block and neighbouring blocks.        -   ii. In one example, all the intervals T_(i) (i being 0 . . .            K−1) are the same, such as L/K. The arithmetic operation ‘/’            is defined as integer division with truncation of the result            toward zero.        -   iii. In one example, (K, L, a₀, T_(i)) is set to (4, 16, 0,            4), or (4, 12, 0, 3) or (4, 8, 0, 1) or (4, 16, 3, 4) or (4,            12, 2, 3), or (4, 8, 1, 2). T_(i) are the same for all i.        -   iv. Such method may be only applied when K is smaller than            L.        -   v. Alternatively, furthermore, when K is larger than or            equal to a threshold, bullet 7.c. may be applied. The            threshold may be defined as L, or it may depend on K or            adaptively changed from block to block. In one example, the            threshold may depend on the number of available motion            candidate in the list before adding a new one from the            look-up table    -   h. In one example, the checking order of K of motion candidates        from the table which includes L candidates may be defined as:        selecting those candidates with index equal to a₀, a₀−T₀,        a₀−T₀−T₁, T₂, . . . a₀−T₀−T₁−T₂, a₀−T₀−T₁−T₂− . . . −T_(K−1) in        order wherein a₀ and T_(i) (i being 0 . . . K−1) are integer        values.        -   i. In one example, ao is set to L−1 (i.e., the last entry of            motion candidate in the table). Alternatively, ao is set to            any integer between L−1−L/K and L−1.        -   ii. In one example, all the intervals T_(i) (i being 0 . . .            K−1) are the same, such as L/K.        -   iii. In one example, (K, L, a₀, T₁) is set to (4, 16, L−1,            4), or (4, 12, L−1, 3) or (4, 8, L−1, 1) or (4, 16, L−4, 4)            or (4, 12, L−3, 3), or (4, 8, L−2, 2). T_(i) are the same            for all i.        -   iv. Such method may be only applied when K is smaller            than L. Alternatively, furthermore, when K is larger than or            equal to a threshold, bullet 7.c. may be applied. The            threshold may be defined as L, or it may depend on K or            adaptively changed from block to block. In one example, the            threshold may depend on the number of available motion            candidate in the list before adding a new one from the            look-up table.    -   i. How many and/or how to select motion candidates from a look        table may depend on the coded information, such as block        size/block shape.        -   i. In one example, for a smaller block size, instead of            choosing the last K motion candidates, the other K motion            candidates (starting not from the last one) may be chosen.        -   ii. In one example, the coded information may be the AMVP or            merge mode.        -   iii. In one example, the coded information may be the affine            mode or non-affine AMVP mode or non-affine merge mode.        -   iv. In one example, the coded information may be the affine            AMVP (inter) mode affine merge mode or non-affine AMVP mode            or non-affine merge mode.        -   v. In one example, the coded information may be Current            Picture Reference (CPR) mode or not CPR mode.        -   vi. Alternatively, how to select motion candidates from a            look-up table may further depend on the number of motion            candidates in the look-up table, and/or number of available            motion candidates in the list before adding a new one from            the look-up table.    -   j. In one example, maximum number of motion candidates in a look        up table to be checked (i.e., which may be added to the        merge/amvp candidate list) may depend on the number of available        motion candidates (denoted by N_(avaiMCinLUT)) in a look up        table, and/or maximally allowed motion candidates (denoted by        NUM_(maxMC)) to be added (which may be pre-defined or signaled),        and/or number of available candidates (denoted by N_(avaiC)) in        a candidate list before checking the candidates from the look up        table.        -   i. In one example, maximum number of motion candidates in            the look up table to be checked is set to minimum value of            (N_(avaiMCinLUT), NUM_(maxMC), N_(avaiC)).        -   ii. Alternatively, maximum number of motion candidates in            the look up table to be checked is set to minimum value of            (N_(avaiMCinLUT), NUM_(maxMC)−N_(avaiC)).        -   iii. In one example, N_(avaiC) denotes the number of            inserted candidates derived from spatial or temporal            (adjacent and/or non-adjacent) neighboring blocks.            Alternatively, furthermore, the number of sub-block            candidates (like AMTVP, STMVP) is not counted in N_(avaiC).        -   iv. NUM_(maxMC) may depend on the coded mode, e.g., for            merge mode and AMVP mode, NUM_(maxMC) may be set to            different values. In one example, for merge mode,            NUM_(maxMC) may be set to 4, 6, 8, 10, etc. al. for AMVP            mode, NUM_(maxMC) may be set to 1, 2, 4, etc. al.        -   v. Alternatively, NUM_(maxMC) may depend on other coded            information, like block size, block shape, slice type etc.            al.    -   k. The checking order of different look up tables is defined in        usage of look up tables in the next subsection.    -   l. The checking process will terminate once the merge/AMVP        candidate list reaches the maximumly allowed candidate numbers.    -   m. The checking process will terminate once the merge/AMVP        candidate list reaches the maximumly allowed candidate numbers        minus a threshold (Th). In one example, Th may be pre-defined as        a positive integer value, e.g., 1, or 2, or 3. Alternatively, Th        may be adaptively changed from block to block. Alternatively, Th        may be signaled in the SPS/PPS/slice header etc. al.        Alternatively, Th may further depend on block shape/block        size/coded modes etc. Alternatively, Th may depend on how many        available candidates before adding the motion candidates from        LUTs.    -   n. Alternatively, it will terminate once the number of added        motion candidates reaches the maximumly allowed motion candidate        numbers. The maximumly allowed motion candidate numbers may be        signaled or pre-defined. Alternatively, the maximumly allowed        motion candidate numbers may further depend on block shape/block        size/coded modes etc.    -   o. One syntax element to indicate the table size as well as the        number of motion candidates (i.e., K=L) allowed to be checked        may be signaled in SPS, PPS, Slice header, tile header.

Example C5: Enabling/disabling the usage look up tables for motioninformation coding of a block may be signalled in SPS, PPS, Sliceheader, tile header, CTU, CTB, CU or PU, region covering multipleCTU/CTB/CU/PUs.

Example C6: Whether to apply prediction from look up tables may furtherdepend on the coded information. When it is inferred not to apply for ablock, additional signaling of indications of the prediction is skipped.Alternatively, when it is inferred not to apply for a block, there is noneed to access motion candidates of look up tables, and the checking ofrelated motion candidates is omitted.

-   -   a. Whether to apply prediction from look up tables may depend on        block size/block shape. In one example, for smaller blocks, such        as 4×4, 8×4 or 4×8 blocks, it is disallowed to perform        prediction from look up tables.    -   b. Whether to apply prediction from look up tables may depend on        whether the block is coded with AMVP or merge mode. In one        example, for the AMVP mode, it is disallowed to perform        prediction from look up tables.    -   c. Whether to apply prediction from look up tables may depend on        the block is coded with affine motion or other kinds of motion        (such as translational motion). In one example, for the affine        mode, it is disallowed to perform prediction from look up        tables.

Example C7: Motion candidates of a look up table in previously codedframes/slices/tiles may be used to predict motion information of a blockin a different frame/slice/tile.

-   -   a. In one example, only look up tables associated with reference        pictures of current block may be utilized for coding current        block.    -   b. In one example, only look up tables associated with pictures        with the same slice type and/or same quantization parameters of        current block may be utilized for coding current block.

Update of look up tables

Example D1: After coding a block with motion information (i.e., IntraBCmode, inter coded mode), one or multiple look up tables may be updated.

-   -   a. In one example, whether to update a look up table may reuse        the rules for selecting look up tables, e.g., when a look up        table could be selected for coding the current block, after        coding/decoding the block, the selected look up table may        further be updated.    -   b. Look up tables to be updated may be selected based on coded        information, and/or positions of the block/LCU.    -   c. If the block is coded with motion information directly        signaled (such as AMVP mode, MMVD mode for normal/affine inter        mode, AMVR mode for normal/affine inter mode), the motion        information for the block may be added to a look up table.        -   i. Alternatively, if the block is coded with motion            information directly inherited from a spatial neighboring            block without any refinement (e.g., spatial merge candidate            without refinement), the motion information for the block            shouldn't be added to a look up table.        -   ii. Alternatively, if the block is coded with motion            information directly inherited from a spatial neighboring            block with refinement (such as DMVR, FRUC), the motion            information for the block shouldn't be added to any look up            table.        -   iii. Alternatively, if the block is coded with motion            information directly inherited from a motion candidate            stored in a look up table, the motion information for the            block shouldn't be added to any look up table.        -   iv. In one example, such motion information may be directly            added to the look up table, such as to the last entry of the            table or to the entry which is used for storing the next            available motion candidate.        -   v. Alternatively, such motion information may be directly            added to the look up table without pruning, e.g., without            any pruning.        -   vi. Alternatively, such motion information may be used to            reorder the look up table.        -   vii. Alternatively, such motion information may be used to            update the look up table with limited pruning (e.g.,            compared to the latest one in the look up table).    -   d. M (M>=1) representative position within the block is chosen        and the motion information associated with the representative is        used to update look up tables.        -   i. In one example, the representative position is defined as            one of the four corner positions (e.g., C0−C3 in FIG. 26)            within the block.        -   ii. In one example, the representative position is defined            as the center position (e.g., Ca−Cd in FIG. 26) within the            block.        -   iii. When sub-block prediction is disallowed for block, M is            set to 1.        -   iv. When sub-block prediction is allowed for block, M could            be set to 1 or total number of sub-blocks or any other value            between [1, number of sub-blocks] exclusively.        -   v. Alternatively, when sub-block prediction is allowed for            block, M could be set to 1 and the selection of a            representative sub-block is based on            -   1. the frequency of utilized motion information,            -   2. whether it is a bi-prediction block            -   3. based on the reference picture index/reference                picture            -   4. motion vector differences compared to other motion                vectors (e.g., selecting the maximum MV differences)            -   5. other coded information.    -   e. When M (M>=1) sets of representative positions are selected        to update look up tables, further conditions may be checked        before adding them as additional motion candidates to look up        tables.        -   i. Pruning may be applied to the new sets of motion            information to the existing motion candidates in the look up            table.        -   ii. In one example, a new set of motion information            shouldn't be identical to any or partial of existing motion            candidates in the look up table.        -   iii. Alternatively, for same reference pictures from a new            set of motion information and one existing motion candidate,            the MV difference should be no smaller than one/multiple            thresholds. For example, horizontal and/or vertical            component of the MV difference should be larger than 1-pixel            distance.        -   iv. Alternatively, the new sets of motion information are            only pruned with the last K candidates or the first K%L            existing motion candidates when K>L to allow reactivating            the old motion candidates.        -   v. Alternatively, no pruning is applied.    -   f. If M sets of motion information are used to update a look up        table, the corresponding counter should be increased by M.    -   g. Suppose a counter of a look up table to be updated is denoted        by K before coding the current block, after coding the block,        for one selected set of motion information (with methods        mentioned above0, it is added as an additional motion candidate        with index equal to K%L (wherein L is the look up table size).        Examples are shown in FIG. 27A and 27B        -   i. Alternatively, it is added as an additional motion            candidate with index equal to min(K+1, L−1). Alternatively,            furthermore, if K>=L, the first motion candidate (index            equal to 0) is removed from the look-up table, and the            following K candidates indices are reduced by 1.        -   ii. For above both methods (either adding the new motion            candidate to entry index equal to K%L or adding it with            index equal to min(K+1, L−1)), they are trying to keep the            latest few sets of motion information from previously coded            blocks regardless whether there are identical/similar motion            candidates.        -   iii. Alternatively, when adding a new set of motion            information as a motion candidate to a LUT, redundancy            checking is firstly applied. In this case, the LUT will keep            the latest several sets of motion information from            previously coded blocks, however, redundant ones may be            removed from LUTs. Such a method is called            redundancy-removal based LUT updating method.            -   1. If there are redundant motion candidates in the LUT,                the counter associated with the LUT may be not increased                or decreased.            -   2. The redundant checking may be defined as the pruning                process in merge candidate list construction process,                e.g., checking whether the reference pictures/reference                picture indices are the same, and motion vector                differences are within a range or identical.            -   3. If there is a redundant motion candidate found in a                LUT, the redundant motion candidate is moved from its                current position to the last one of the LUT.                -   a. Similarly, if there is a redundant motion                    candidate found in a LUT, this redundant motion                    candidate is removed from the LUT. In addition, all                    the motion candidates inserted to LUT after the                    redundant motion candidate move forward to refill                    the removed entry of the redundant motion candidate.                    After the shifting, the new motion candidate is                    added to the LUT.                -   b. In this case, the counter is kept unchanged.                -   c. Once a redundant motion candidate is identified                    in a LUT, the redundant checking process is                    terminated.            -   4. Multiple redundant motion candidates may be                identified. In this case, all of them are removed from                the LUT. In addition, all of the remaining motion                candidates may move forward in order.                -   a. In this case, the counter is decreased by (number                    of redundant motion candidates minus 1).                -   b. The redundant checking process is terminated                    after identifying maxR redundant motion candidates                    (maxR is a positive integer variable).            -   5. The redundancy checking process may start from the                first to the last motion candidate (i.e., in the order                of added to LUTs, in the order of decoding process of                blocks where motion information is from).            -   6. Alternatively, when there are redundant motion                candidates in LUT, instead of removing one or multiple                of redundant ones form LUTs, virtual motion candidates                may be derived from redundant ones and the virtual                motion candidates may be used to replace the redundant                ones.                -   a. Virtual motion candidates may be derived from a                    redundant motion candidate by adding offset(s) to                    horizontal and/or vertical component of one or                    multiple motion vectors; or average of two motion                    vectors if pointing to the same reference pictures.                    Alternatively, the virtual motion candidate may be                    derived from any function with motion vectors in the                    look up table as the input. Exemplary functions are:                    Adding two or motion vectors together; Averaging two                    or more motion vectors. The motion vectors may be                    scaled before being input into the function.                -   b. Virtual motion candidates may be added to the                    same position as the redundant motion candidates.                -   c. Virtual motion candidates may be added before all                    the other motion candidates (e.g., starting from                    smallest entry indices, like zero).                -   d. In one example, it is applied only under certain                    conditions, such as when the current LUT is not                    full.            -   7. The redundancy-removal based LUT updating method may                be invoked under certain conditions, such as                -   a. the current block is coded with merge mode,                -   b. the current block is coded with AMVP mode but                    with at least one component of MV difference is                    non-zero;                -   c. the current block is or is not coded with                    sub-block based motion prediction/motion                    compensation methods (e.g., not coded with affine                    mode)                -   d. the current block is coded with merge mode and                    the motion information is associated with a certain                    type (e.g., from the spatial neighboring blocks,                    from the left neighboring block, from the temporal                    block)    -   h. After encoding/decoding one block, one or more look-up tables        may be updated by just inserting the M sets of motion        information to the end of the table, i.e., after all existing        candidates.        -   i. Alternatively, furthermore, some existing motion            candidates in the table may be removed.            -   1. In one example, if the table is full after inserting                the M sets of motion information, the first several                entries of motion candidates may be removed from the                table.            -   2. In one example, if the table is full before inserting                the M sets of motion information, the first several                entries of motion candidates may be removed from the                table.        -   ii. Alternatively, furthermore, if the block is coded with a            motion candidate from a table, the motion candidates in the            table may be reordered so that the selected motion candidate            is put to the last entry of the table.    -   i. In one example, before encoding/decoding a block, a look-up        table may include motion candidates denoted by HMVP0, HMVP1,        HMVP2, HMVP_(K−1), HMVP_(K), HMVP_(K+1), . . . , HMVP_(L−1),        wherein HMVP_(i) denotes the i-th entry in the look-up table. If        the block is predicted from HMVP_(K) (K is within the range [0,        L−1], inclusively), after encoding/decoding this block, the        look-up table is re-ordered to: HMVP₀, HMVP₁, HMVP₂, . . . ,        HMVP_(K−1), HMVP_(K), HMVP_(K+1), HMVP_(L−1), HMVP_(K).    -   j. The look-up table may be emptied after coding one        intra-constrained block.    -   k. If an entry of motion information is added into the lookup        table, more entries of motion information may also be added into        the table by derivation from the motion inforamtion. In this        case, the counter associated with the look up table may be        increased more than 1.        -   i. In one example, the MV of an entry of motion information            is scaled and put into the table;        -   ii. In one example, the MV of an entry of motion information            is added by (dx, dy) and put into the table;        -   iii. In one example, the average of MVs of two or more            entries of motion information is calculated and put into the            table.

Example D2: If one block is located at a picture/slice/tile border,updating of look up tables may be always disallowed.

Example D3: Motion information of above LCU rows may be disabled to codethe current LCU row.

a. In this case, at the beginning of a new slice/tile/LCU row, thenumber of available motion candidates may be reset to 0.

Example D4: At the beginning of coding a slice/tile with a new temporallayer index, the number of available motion candidates may be reset to0.

Example D5: The look up table may be continuously updated with oneslice/tile/LCU row/slices with same temporal layer index.

-   -   a. Alternatively, the look up table may be updated only after        coding/decoding each S (S>=1) CTUs/CTBs/CUs/CBs or after        coding/decoding a certain region (e.g., size equal to 8×8 or        16×16).    -   b. Alternatively, the look up table may be updated only after        coding/decoding each

S (S>=1) blocks (e.g., CUs/CBs) with certain modes (e.g., S inter-codedblocks). Alternatively, the look up table may be updated only aftercoding/decoding each S (S>=1) inter-coded blocks (e.g., CUs/CBs) whichare not coded with sub-block based motion prediction/motion compensationmethod (e.g., not coded with affine and/or ATMVP mode).

-   -   c. Alternatively, the look up table may be updated only when the        left-top coordinate of the coded/decoded block satisfies some        conditions. For example, the look up table is updated only when        (x&M==0)&&(y&M==0), where (x, y) is left-top coordinate of the        coded/decoded block. M is an integer such as 2, 4, 8, 16, 32, or        64.    -   d. Alternatively, one look up table may stop updating once it        reaches a maximumly allowed counter.    -   e. In one example, the counter may be predefined. Alternatively,        it be signalled in Video Parameter Set (VPS), Sequence Parameter        Set (SPS), Picture Parameter Set (PPS), Slice header, tile        header, Coding Tree Unit (CTU), Coding Tree Block (CTB), Coding        Unit (CU) or Prediction Unit (PU), region covering multiple        CTU/CTB/CU/PUs.

Example D6: Look up table updating process may be invoked withindifferent procedures.

-   -   a. In one example, for a block coded with merge mode, the look        up table updating process may be invoked after decoding the        merge candidate or after constructing the merge list or after        decoding the motion information with and/or without refinement.    -   b. In one example, for a block coded with AMVP mode, the look up        table updating process may be invoked after decoding the motion        information with and/or without refinement.    -   c. When and/or how to update the look up table may depend on the        coded mode, block dimension, video processing data unit, low        delay check, etc.        -   i. In one example, when one block is coded with AMVP mode,            look up table may be directly updated without pruning.        -   ii. Alternatively, when one block is coded with merge mode,            look up table may be updated with pruning.        -   iii. Alternatively, when one block is coded with merge mode            and its motion information is derived from spatial and/or            temporal blocks, look up table may be updated with pruning.        -   iv. Alternatively, when one block is coded with merge mode            and its motion information is derived from motion candidates            in a look up table, look up table may be reordered without            pruning.        -   v. Alternatively, when one block is coded with merge mode            and its motion information is derived from virtual            candidates (e.g., combined bi, pairwise, zero motion vector            candidates) in a look up table, look up table may not be            updated.        -   vi. Alternatively, when one block is coded with sub-block            merge mode and/or triangular merge mode, look up table may            not be updated.        -   vii. Alternatively, when one block is coded with the merge            with motion vector differences (MMVD) mode and its motion            information is derived from spatial and/or temporal blocks,            look up table may be directly updated.        -   viii. In one example, when one block is coded with            illumination compensation (IC) mode and/or Overlapped Block            Motion Compensation (OBMC) mode and/or Decode-side Motion            Vector Derivation (DMVD) mode, look up table may not be            updated. Alternatively, when one block is coded with such a            mode, look up table may be updated.

Example D7: Whether to reset the look up tables may further depend onthe indication of enabling (or disabling) prediction crossing tiles.

-   -   a. In one example, if such an indication indicates prediction        crossing tiles is disallowed, look up tables have to be reset        (e.g., emptied) before coding a new tile.    -   b. In one example, such an indication indicates prediction        crossing tiles is allowed, there is no need to reset look up        tables (e.g., emptied) before coding a new tile. That is, the        look up tables for coding a second tile may depend on those        tables used for coding a first tile.

Example D8: Whether to enable adaptive loop filter (ALF) temporalprediction (or prediction/inheritance of ALF filters from a differenttile) may further depend on the indication of enabling (or disabling)prediction crossing tiles.

-   -   a. In one example, if such an indication indicates prediction        crossing tiles is disallowed, ALF temporal prediction is        disallowed.    -   b. In one example, such an indication indicates prediction        crossing tiles is allowed, ALF temporal prediction may be        enabled.

Example D9: When shared merge list (or other kinds of shared motioncandidates list/or shared intra mode information or other sharedinformation) is enabled for a merge sharing node, the updating of lookup tables may be performed in the following ways:

-   -   a. One of representative coded block (e.g., leaf coding unit)        may be selected to update the look up tables.        -   ii. In one example, it is defined as the last coded block in            decoding order.        -   iii. Alternatively, it is defined as the last coded block            that satisfy the conditions for look up table updating (such            as the last coded block with non-affine and non-ATMVP inter            mode).        -   iv. In one example, it is defined as the first coded block            in decoding order under the parent node.        -   v. Alternatively, it is defined as the first coded block            that satisfy the conditions for look up table updating (such            as the last coded block with non-affine and non-ATMVP,            non-triangular inter mode) under the parent node.    -   b. More than one representative coded blocks (e.g., leaf coding        unit) may be selected to update the look up tables.        -   vi. In one example, multiple sets of coded information            associated with those representative coded blocks may be            used to update the look up tables wherein multiple entries            of a look up table may be updated accordingly.        -   vii. In one example, multiple sets of coded information            associated with those representative coded blocks may be            used to update the look up tables wherein multiple look up            tables may be updated accordingly.        -   viii. In one example, those representative coded blocks may            be checked in a certain order to determinate whether to be            used to update one or multiple look up tables.        -   ix. In one example, those representative coded blocks may be            defined as the first and the last coded block under the            parent node.    -   c. Updating of look up tables may be always disabled.

Example D10: For all above bullets, the look up tables indicate thecoded information or information derived from coded information frompreviously coded blocks in a decoding order.

-   -   a. A look up table may include the translational motion        information, or affine motion information, or affine model        parameters, or intra mode information, or illumination        compensation information, etc. al.    -   b. Alternatively, a look up table may include at least two kinds        of information, such as translational motion information, or        affine motion information, or affine model parameters, or intra        mode information, or illumination compensation information, etc.        al.

Additional Example Embodiments

A history-based MVP (HMVP) method is proposed wherein a HMVP candidateis defined as the motion information of a previously coded block. Atable with multiple HMVP candidates is maintained during theencoding/decoding process. The table is emptied when a new slice isencountered. Whenever there is an inter-coded block, the associatedmotion information is added to the last entry of the table as a new HMVPcandidate. The overall coding flow is depicted in FIG. 31.

In one example, the table size is set to be L (e.g., L=16 or 6, or 44),which indicates up to L HMVP candidates may be added to the table.

In one embodiment (corresponding to example 11.g.i), if there are morethan L HMVP candidates from the previously coded blocks, aFirst-In-First-Out (FIFO) rule is applied so that the table alwayscontains the latest previously coded L motion candidates. FIG. 32depicts an example wherein the FIFO rule is applied to remove a HMVPcandidate and add a new one to the table used in the proposed method.

In another embodiment (corresponding to invention 11.g.iii), wheneveradding a new motion candidate (such as the current block is inter-codedand non-affine mode), a redundancy checking process is applied firstlyto identify whether there are identical or similar motion candidates inLUTs.

Some examples are depicted as follows:

FIG. 33A shows an example when the LUT is full before adding a newmotion candidate.

FIG. 33B shows an example when the LUT is not full before adding a newmotion candidate.

FIG. 33A and 33B together show an example of redundancy-removal basedLUT updating method (with one redundancy motion candidate removed).

FIG. 34A and 34B show example implementation for two cases of theredundancy-removal based LUT updating method (with multiple redundancymotion candidates removed, 2 candidates in the figures)

FIG. 34A shows an example case of when the LUT is full before adding anew motion candidate.

FIG. 34B shows an example case of When the LUT is not full before addinga new motion candidate

HMVP candidates could be used in the merge candidate list constructionprocess. All HMVP candidates from the last entry to the first entry (orthe last K0 HMVP, e.g., K0 equal to 16 or 6) in the table are insertedafter the TMVP candidate. Pruning is applied on the HMVP candidates.Once the total number of available merge candidates reaches the signaledmaximally allowed merge candidates, the merge candidate listconstruction process is terminated. Alternatively, once the total numberof added motion candidates reaches a given value, the fetching of motioncandidates from LUTs is terminated.

Similarly, HMVP candidates could also be used in the AMVP candidate listconstruction process. The motion vectors of the last K1 HMVP candidatesin the table are inserted after the TMVP candidate. Only HMVP candidateswith the same reference picture as the AMVP target reference picture areused to construct the AMVP candidate list. Pruning is applied on theHMVP candidates. In one example, K1 is set to 4.

REFERENCES

-   [1] “Overview of the High Efficiency Video Coding (HEVC) Standard”,    Gary J. Sullivan, Jens-Rainer Ohm, Woo-Jin Han, and Thomas Wiegand,    IEEE Transactions on Circuits and Systems for Video Technology, Vol.    22, No. 12, December 2012.-   [2] “Overview of the H.264/AVC video coding standard”, Ajay Luthra,    Pankaj Topiwala, Proceedings of SPIE Vol. 5203 Applications of    Digital Image Processing XXVI.-   [3] J. Chen, E. Alshina, G. J. Sullivan, J.-R. Ohm, J. Boyce,    “Algorithm description of Joint Exploration Test Model 7 (JEM7),”    JVET-G1001, Aug. 2017.-   [4] JEM-7.0:    https://jvet.hhi.fraunhofer.de/svn/svn_HMJEMSoftware/tags/HM-16.6-JEM-7.0.-   [5] H.265/HEVC, https://www.itu.int/rec/T-REC-H.265-   [6] “Multi-Type-Tree”, JVET-D0117-   [7] International Patent Application WO2016/091161-   [8] “Description of SDR, HDR and 360° video coding technology    proposal by Qualcomm and Technicolor—low and high complexity    versions”, JVET-J0021.

FIG. 28A is a block diagram of a video processing apparatus 2800. Theapparatus 2800 may be used to implement one or more of the methodsdescribed herein. The apparatus 2800 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 2800 may include one or more processors 2802, one or morememories 2804 and video processing hardware 2806. The processor(s) 2802may be configured to implement one or more methods described in thepresent document. The memory (memories) 2804 may be used for storingdata and code used for implementing the methods and techniques describedherein. The video processing hardware 2806 may be used to implement, inhardware circuitry, some techniques described in the present document.

FIG. 28B is another example of a block diagram of a video processingsystem in which disclosed techniques may be implemented. FIG. 28B is ablock diagram showing an example video processing system 3100 in whichvarious techniques disclosed herein may be implemented. Variousimplementations may include some or all of the components of the system3100. The system 3100 may include input 3102 for receiving videocontent. The video content may be received in a raw or uncompressedformat, e.g., 8 or 10 bit multi-component pixel values, or may be in acompressed or encoded format. The input 3102 may represent a networkinterface, a peripheral bus interface, or a storage interface. Examplesof network interface include wired interfaces such as Ethernet, passiveoptical network (PON), etc. and wireless interfaces such as Wi-Fi orcellular interfaces.

The system 3100 may include a coding component 3104 that may implementthe various coding or encoding methods described in the presentdocument. The coding component 3104 may reduce the average bitrate ofvideo from the input 3102 to the output of the coding component 3104 toproduce a coded representation of the video. The coding techniques aretherefore sometimes called video compression or video transcodingtechniques. The output of the coding component 3104 may be eitherstored, or transmitted via a communication connected, as represented bythe component 3106. The stored or communicated bitstream (or coded)representation of the video received at the input 3102 may be used bythe component 3108 for generating pixel values or displayable video thatis sent to a display interface 3110. The process of generatinguser-viewable video from the bitstream representation is sometimescalled video decompression. Furthermore, while certain video processingoperations are referred to as “coding” operations or tools, it will beappreciated that the coding tools or operations are used at an encoderand corresponding decoding tools or operations that reverse the resultsof the coding will be performed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include SATA (serial advanced technology attachment), PCI,IDE interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

In some embodiments, the video coding methods may be implemented usingan apparatus that is implemented on a hardware platform as describedwith respect to FIG. 28A or 28B.

FIG. 29 is a flowchart for an example of a video decoding method 2900.The method 2900 includes, at step 2902, determining, whether to use atemporal prediction for obtaining an adaptive loop filter for aconversion between a current video block of a video and a codedrepresentation of the video, based on whether a cross-tile prediction isenabled. The method 2900 further includes, at step 2904, performing theconversion using an adaptive loop filter that is obtained based on thedetermining.

FIG. 30 shows a flowchart for an example of video decoding method 3000.The method 3000 includes, at step 3002, determining whether a sharing ofmerge list information is enabled for a merge sharing node thatcorresponds to an ancestor node in a coding unit split tree to allowleaf coding units of the ancestor node in the coding unit split tree touse the merge list information. The method 3000 further includes, atstep 3004, performing a conversion between a current video block of avideo and a coded representation of the video based on the determining.

With respect to methods 2900 and 3000, in some embodiments, the motioninformation includes at least one of: a prediction direction, areference picture index, motion vector values, intensity compensationflag, affine flag, motion vector difference precision, and motion vectordifference value. Further, the motion information may further includeblock position information indicating source of the motion information.In some embodiments, the video block may be a CU or a PU and the portionof video may correspond to one or more video slices or one or more videopictures.

In some embodiments, each LUT includes an associated counter, whereinthe counter is initialized to a zero value at beginning of the portionof video and increased for each encoded video region in the portion ofthe video. The video region comprises one of a coding tree unit, acoding tree block, a coding unit, a coding block or a prediction unit.In some embodiments, the counter indicates, for a corresponding LUT, anumber of motion candidates that were removed from the correspondingLUT. In some embodiments, the set of motion candidates may have a samesize for all LUTs. In some embodiments, the portion of video correspondsto a slice of video, and wherein the number of LUTs is equal to N*P,wherein N is an integer representing LUTs per decoding thread, and P isan integer representing a number of Largest Coding Unit rows or a numberof tiles in the slice of video. Additional details of the methods 2900and 3000 are described in the examples provided in Section 4 and theexamples listed below.

1. A method for video processing, comprising: determining, whether touse a temporal prediction for obtaining an adaptive loop filter for aconversion between a current video block of a video and a codedrepresentation of the video, based on whether a cross-tile prediction isenabled; and performing the conversion using an adaptive loop filterthat is obtained based on the determining.

2. The method of example 1, wherein the temporal prediction is not usedfor obtaining the adaptive loop filter due to the cross-tile predictionnot being enabled.

3. The method of example 1, wherein the temporal prediction is used forobtaining the adaptive loop filter due to the cross-tile predictionbeing allowed.

4. A method for video processing, comprising: determining whether asharing of merge list information is enabled for a merge sharing nodethat corresponds to an ancestor node in a coding unit split tree toallow leaf coding units of the ancestor node in the coding unit splittree to use the merge list information; and performing a conversionbetween a current video block of a video and a coded representation ofthe video based on the determining.

5. The method of example 4, wherein updating a motion candidate table isenabled or disabled during the conversion.

6. The method of example 4, wherein the merge list information includesat least one of a merge list, a motion candidate list, an intra modeinformation, or any typed information.

7. The method of example 1, wherein a single representative coded blockis selected to update a motion candidate table.

8. The method of example 7, wherein the single representative codedblock is selected as a last coded block according to a decoding order.

9. The method of example 7, wherein the single representative codedblock is selected as a last coded block that that satisfies a conditionfor updating the motion candidate table.

10. The method of example 9, wherein the condition for updating themotion candidate table requires that the last coded block is coded witha non-affine and non-ATMVP (alternative temporal motion vectorprediction) inter mode, wherein the ATMVP mode modifies motion vectorstemporal motion vector prediction (TMVP) by fetching multiple sets ofmotion information from blocks smaller than a current coding unitincluding the current video block.

11. The method of example 7, wherein the single representative codedblock is selected as a first coded block according to a decoding orderunder a parent node.

12. The method of example 7, wherein the single representative codedblock is selected as a first coded block that that satisfies a conditionfor updating the motion candidate table.

13. The method of example 12, wherein the condition for updating themotion candidate table requires that the first coded block is coded witha non-affine and non-ATMVP (alternative temporal motion vectorprediction) inter mode, wherein the ATMVP mode modifies motion vectorstemporal motion vector prediction (TMVP) by fetching multiple sets ofmotion information from blocks smaller than a current coding unitincluding the current video block.

14. The method of example 1, wherein multiple representative codedblocks are selected to update a motion candidate table.

15. The method of example 14, wherein multiple sets of coded informationassociated with the multiple representative coded blocks are used toupdate multiple entries of the motion candidate table.

16. The method of example 14, wherein the performing of the conversionfurther includes updating an additional motion candidate table andwherein multiple sets of coded information associated with the multiplerepresentative coded blocks are used to update the motion candidatetable and the additional motion candidate table.

17. The method of example 14, wherein the multiple representative codedblocks are checked in a certain order to determine whether to be used toupdate the motion candidate table.

18. The method of example 14, wherein the multiple representative codedblocks are selected as a first or last coded block under a parent node.

19. The method of example 2, wherein updating of a motion candidatetable is always disabled.

20. The method of any of examples 2-16, wherein the motion candidatetable indicates coded information or information derived from codedinformation from previously coded blocks in a decoding order.

21. The method of example 20, wherein the motion candidate tableincludes at least one of translational motion information, affine motioninformation, affine model parameters, intra mode information, orillumination compensation information.

22. The method of any of examples 1 to 21, wherein the performing of theconversion includes generating the coded representation from the currentvideo block.

23. The method of any of examples 1 to 21, wherein the performing of theconversion includes generating the current video block from the codedrepresentation.

24. An apparatus in a video system comprising a processor and anon-transitory memory with instructions thereon, wherein theinstructions upon execution by the processor, cause the processor toimplement the method recited in one or more of examples 1 to 23.

25. A computer program product stored on a non-transitory computerreadable media, the computer program product including program code forcarrying out the method recited in one or more of examples 1 to 23.

From the foregoing, it will be appreciated that specific embodiments ofthe presently disclosed technology have been described herein forpurposes of illustration, but that various modifications may be madewithout deviating from the scope of the invention. Accordingly, thepresently disclosed technology is not limited except as by the appendedclaims.

The disclosed and other embodiments, modules and the functionaloperations described in this document can be implemented in digitalelectronic circuitry, or in computer software, firmware, or hardware,including the structures disclosed in this document and their structuralequivalents, or in combinations of one or more of them. The disclosedand other embodiments can be implemented as one or more computer programproducts, i.e., one or more modules of computer program instructionsencoded on a computer readable medium for execution by, or to controlthe operation of, data processing apparatus. The computer readablemedium can be a machine-readable storage device, a machine-readablestorage substrate, a memory device, a composition of matter effecting amachine-readable propagated signal, or a combination of one or morethem. The term “data processing apparatus” encompasses all apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, or multiple processors or computers.The apparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them. A propagated signal is an artificially generated signal, e.g.,a machine-generated electrical, optical, or electromagnetic signal, thatis generated to encode information for transmission to suitable receiverapparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any invention or of what may beclaimed, but rather as descriptions of features that may be specific toparticular embodiments of particular inventions. Certain features thatare described in this patent document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A method for processing video data, comprising:determining whether a sharing of merge list information is enabled for amerge sharing node that corresponds to an ancestor node in a coding unitsplit tree to allow leaf coding units of the ancestor node in the codingunit split tree to use the merge list information; and performing aconversion between a current video block of a video and a bitstream ofthe video based on the determining.
 2. The method of claim 1, whereinupdating a motion candidate table is selectively enabled or disabledduring the conversion.
 3. The method of claim 1, wherein the merge listinformation includes at least one of a merge list, a motion candidatelist, an intra mode information, or any typed information.
 4. The methodof claim 2, wherein a single representative coded block is selected toupdate the motion candidate table.
 5. The method of claim 4, wherein thesingle representative coded block is selected as a last coded blockaccording to a decoding order.
 6. The method of claim 4, wherein thesingle representative coded block is selected as a last coded block thatthat satisfies a condition for updating the motion candidate table. 7.The method of claim 6, wherein the condition for updating the motioncandidate table requires that the last coded block is coded with anon-affine and non-ATMVP (alternative temporal motion vector prediction)inter mode, wherein the ATMVP mode modifies motion vectors temporalmotion vector prediction (TMVP) by fetching multiple sets of motioninformation from blocks smaller than a current coding unit including thecurrent video block.
 8. The method of claim 4, wherein the singlerepresentative coded block is selected as a first coded block accordingto a decoding order under a parent node.
 9. The method of claim 4,wherein the single representative coded block is selected as a firstcoded block that that satisfies a condition for updating the motioncandidate table.
 10. The method of claim 9, wherein the condition forupdating the motion candidate table requires that the first coded blockis coded with a non-affine and non-ATMVP (alternative temporal motionvector prediction) inter mode, wherein the ATMVP mode modifies motionvectors temporal motion vector prediction (TMVP) by fetching multiplesets of motion information from blocks smaller than a current codingunit including the current video block.
 11. The method of claim 2,wherein multiple representative coded blocks are selected to update themotion candidate table.
 12. The method of claim 11, wherein multiplesets of coded information associated with the multiple representativecoded blocks are used to update multiple entries of the motion candidatetable.
 13. The method of claim 11, wherein the performing of theconversion further includes updating an additional motion candidatetable and wherein multiple sets of coded information associated with themultiple representative coded blocks are used to update the motioncandidate table and the additional motion candidate table.
 14. Themethod of claim 11, wherein the multiple representative coded blocks arechecked in a certain order to determine whether to be used to update themotion candidate table.
 15. The method of claim 11, wherein the multiplerepresentative coded blocks are selected as a first or last coded blockunder a parent node.
 16. The method of claim 2, wherein updating of themotion candidate table is always disabled.
 17. The method of any ofclaim 1, wherein the conversion includes encoding the current videoblock into the bitstream.
 18. The method of any of claim 1, wherein theconversion includes decoding the current video block from the bitstream.19. An apparatus for processing video data comprising a processor and anon-transitory memory with instructions thereon, wherein theinstructions upon execution by the processor, cause the processor to:determine whether a sharing of merge list information is enabled for amerge sharing node that corresponds to an ancestor node in a coding unitsplit tree to allow leaf coding units of the ancestor node in the codingunit split tree to use the merge list information; and perform aconversion between a current video block of a video and a bitstream ofthe video based on the determining.
 20. A non-transitorycomputer-readable recording medium storing a bitstream which isgenerated by a method performed by a video processing apparatus, whereinthe method comprises: determining whether a sharing of merge listinformation is enabled for a merge sharing node that corresponds to anancestor node in a coding unit split tree to allow leaf coding units ofthe ancestor node in the coding unit split tree to use the merge listinformation; and generating the bitstream based on the determining.